LSX G-body Swap Write Up


Master Mechanic
Jan 12, 2013
SE South Dakota
So you want to take the plunge, and swap in a LSX engine into your G-body. This is a writeup on core parts you will need to do the swap. The question has been asked A LOT lately, so I thought it would be best to make this write up for everyone.

Finding an Engine

First thing first finding an engine. It used to be easy to walk into just about any salvage yard, and pick up a low mileage 4.8. 5.3, or 6.0 with the: computer, accessories, starter, wire harness, and coil packs for $1000.00 sometimes less. Now it seems they are trying to squeeze every last penny out of us.

This past winter, I went to the local yard to pick up a 5.3 for the swap I am doing in my Cutlass. The only ones they had were high mileage (150K plus.). I negotiated what I thought was a good price due to the miles on it ($600.00 range). When I went around to the yard to get it, I was really disappointed. It didn't come with the computer, wire harness, accessories, starter, or even the oil fill pipe. The throttle body was drive by wire, and it didn't even include the gas pedal with it(very important if your going to use it that way). It did have the coil packs on it.

I inquired to why this was, and they replied that if I wanted that stuff it would be an extra $600.00! I couldn't believe it. I said they used to come with all the above stuff. Their replay was, since LS swaps were so popular now, that they are now charging extra for it.

I thought it was just this yard doing this, so I called several in my area. The other ones were doing the same thing or worse. One was also charging a $100.00 core charge for the engine on top of everything else. They also had a 6.0 with 220K plus miles on it, and they wanted $1200.00 for it plus the core charge, and accessories!

To avoid getting drilled by the yards, the best place I have found to get a hold of a good priced one is on your local craigslist, or by word of mouth from guys around town. If you do get one from a yard, make sure it comes with everything you want for the price you negotiated. Don't get caught with your pants down like I did.

Oil Pans

If you got your LS engine out of a truck, you will need to change out the oil pan. The most popular pans for the G-body are a muscle car swap pan kit (GM part number 19212593), and the Cadillac CTSV pan(GM Part number 12605814) . The CTSV and muscle car pans are a direct fit into a G-body. The CTSV pan has the best ground clearance. The next best would be the muscle car swap pan. A LS1 F-body pan can also be used, but the cross-member in the engine bay will need to be modified for it to fit. The truck pan will fit in the G-body, but the rear sump will hang very low to the ground. I used the muscle car swap kit on my car, since it comes with everything you need (pan, gasket, bolts, windage tray, pickup, and dipstick). You would have to piece together everything you need for the CTSV pan, unless you find someone parting it all out as a kit. The included link has all the oil pans used on LS engines, measurements, and part numbers. ... -pans.html

Motor Mounts

The factory LS mounts that bolt to the block of the engine will not work with the G-body's factory frame mounts. Lucky for us there are adapter plates we can buy to fix this problem. From the factory the LS engine mounts a couple of inches forward from the original gen 1 engines. To get the engine to sit in the old engine's original position, you will need 1” setback adapter plates. The plates will allow you to bolt gen 1 SBC clam shell mounts to the plates. On the frame side you will need SBC frame pads. If you G-body came with an Olds\Buick V8 or has a V6 , you will need to replace the frame pads. For my car, I got frame pads for a 87 Monte Carlo SS with a 305 V8. Many companies now make LS swap adapter plates. The best price I have found for them has been on Ebay. The go for around $40-$50.


If you want to use your TH350, 200-4R or any other old school transmission, you will need to get a spacer (GM part number 12563532) for the LS engines flex plate. This is so the torque converter has the proper spacing in relation to the rear of the crank. You will also need longer flex plate bolts (GM part number 19257940). To bolt the converter on, you will also have to egg out the holes in the flex plate, since the later transmissions have a slightly different converter bolt pattern. Old school transmissions bolt to the LS engine block without any adapters.


Stock truck accessories will clear a g-body hood if you use the 105 amp alternator. Some of the power steering pump pulleys will not clear the g-body steering box. You can swap the pulley out for a smaller one. I have been told that the pulleys are available at your local parts store under the doorman brand name. F-body accessories will also work, and give more hood clearance, but are hard to find in the yards. When you do find a set, they usually want quite a bit for them. The a/c compressor will not clear the passenger side frame rail. If you want a/c, you will have to notch the frame to get it to fit. The a/c compressor mounts in the same lower right side location on the truck and f-body system.


Now that you have the engine sitting between the fenders, its time to gets some exhaust on it. You first have to decide if you want to put manifolds on it or headers. If you want to use manifolds, truck manifolds will not clear. You will need either f-body or Corvette manifolds. F-body ones are easy to find, since a lot of guys ditch them for headers.

If you decide on headers, there are a few options out there. Shorty headers for a LS S-10 truck swap will fit a g-body. They actually fit really well. For long tubes, headman and BRP make a set. They also can run north of $600.00. A set of Pacesetter long tubes for 98-02 f-body will also fit. The Pacesetter ceramic coated ones can be found used for around $250.00. The pacesetter headers may need slight mods for them to fit correctly. One of the tubes may hit the frame on the passenger side, and the collector on the drivers side may kick out toward the frame at an angle. You can heat up the drivers side, and bend it straight. For the passenger side, a lot of guys dent the offending tube with a hammer. You can also cut the tube, reroute and reweld it.

Carb or EFI

carb or efi? The easiest way to get your car on the road is to run a carb setup. To run a carb you will need a ignition box to run the coils and engine timing, carb intake, and carb. Edelbrock does make a carb swap kit for around $700.00. I don't recommend using it. You can piece it out for cheaper, and get a better ignition box to boot.
The box you want to get is either a MSD-6010 or MSD-6012. The box you need, depends on the relector wheel your crank uses. The 6010 is for cranks that have a 24 tooth wheel, and the 6012 is for cranks that have a 58 tooth wheel. The 6010\6012 box is computer programmable, has a nitrous timing retard, and a two step in it. The Edelbrock unit is not programmable, and uses pills instead of computer programming.

Edelbrock has basically two intake options. The performer RPM and the Victor JR. You will then need a good carb. Another thing to consider if using a carb set up is the cam your running in the engine. The factory fuel injection cam has about 115-116 LSA, not all that carb friendly. Its recommended that a cam with 110 LSA is used. Edelbrock does have a line of carb friendly cams. You can also get the other major cam companies grind one for you.

Fuel injection is another animal. You will need the ECM, wire harness, fuel injection intake, and gas pedal from your donor car if using the drive by wire throttle body. You will have to get the ECM retuned for your setup, and get the engine wiring harness modified to work with your car. There are a lot of companies that sell modified wire harnesses for your setup. You can also modify the factory one your self. Same goes for tuning the ECM. The software is expensive if you want to do it yourself. The two most popular programs are EFI Live and HP Tuners. They both go for around $600.00.

A little added note. The #8 coil pack may hit the a/c box on the passenger side. You might have to modify the box to get it to clear. I haven’t heard if there are any clearance issues with the heat only setup.

I hope this helps the guys out that are doing or thinking of doing a LS swap into their g-body. There are probably some small odds and ends that I missed, but this writeup should get you well on your way to getting it done. There is also a lot of swap info on the g-body swap thread over on I have included the link. It currently has over 1000 posts and climbing on the subject. ... hread.html
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Reactions: 2 users


Master Mechanic
Thread starter
Jan 12, 2013
SE South Dakota
This is in response of the multiple requests for LSX swap info. I hope the mods will make this a sticky for the guys looking to do the swap.


Royal Smart Person
Nov 14, 2008
Great info!! If using the transdapt 4595 1in setback plates with the stock clamshells you will have stock ls1 alt pulley interference with the gear box... I have heard of using a smaller pulley or relocating the alt. I used this kit from Speedway motors: ... 42493.html
works ok for now with no issues, And if you intend to go fuel injected get a GN fuel tank or any fuel injected fuel tank, fuel pump from: ... 55&eq=&Tp=
and I used the hotwire kit as well: ... 06&eq=&Tp=
this along with a Vette filter and some braided steel lines, and some fittings made it work!! the f body exhaust manifolds work great, though I did relocate the front 02 sensors. The f body factory harness is actually quite easy to mod and I used factory fuseboxes... 8) I kept the stock cats and got it certified by the state without any issues!! I also used my stock g body gauges using the og harness except for the tach... the speedo was kept after using this guy and it kept the stock VSS: BTW awesome guy to work with. :mrgreen:
as for the t56 pedal the infamous JOHN B was also a great to work with as well.. :mrgreen:
I did have to add a NSS switch and a 3rd gen f body clutch reservoir though.. For know that is all but I will probably remember more... :D

Kansas Bu Wagon

G-Body Guru
Jul 9, 2012
Wichita, Ks has complete ctsv oil pan kits for $330. They also have internal and external fuel system kits, brand new standalone wiring harnesses, computer flashing, computers, and drive by wire pedals and accessories.

They have kits for lsx, and ltx swaps. Go check it out.


Master Mechanic
Thread starter
Jan 12, 2013
SE South Dakota
Great info guys. I was hoping people would add to it. Keep it coming.


Feb 11, 2011
I used the BRP mounts. They give you plenty of clearance from the heat/ac box. I went with the corvette accessory drive. no issues with the steering pump. I used an ac compressor relocation bracket to move it up top. HOLLEYS ls swap pan fits great. The sump is flush with the cross member. One thing i wouldn't reccomend is the BRP cross member. They are the most il fitting piece of crap you could imagine. The GFORCE cross members are great.


Rocket Powered Basset Hound
Oct 14, 2008
Gainesville, Fl
Great information, guys. With LS swaps becoming more the norm these days, this thread should probably be a sticky.

Can we see more information on how to identify the various LS type engines?


G-Body Guru
Nov 6, 2010
Lake Wylie,SC
Great write up can't wait to do this swap.

Clone TIE Pilot

Comic Book Super Hero
Aug 14, 2011
Galaxy far far away
I have a question about using older transmissions like the THM2004R behind a LS motor. Can the LS's PCM be modified to run the 2004r's lockup or do you still need an aftermarket lockup kit? I would rather the PCM since even the CCC ECM lockups the trans better than the aftermarket kits do.


Jul 5, 2012
I finished my swap about this time last year . I will throw in ... for a fuel tank you can use a 92-94 roadmaster wagon fuel tank if you have an elcamino as it has the side fill . I think its 27 gallon and you need larger straps but it fits . I had to extend the fill/vent hose slightly and i used my old cap and fill end cut off the old tank. Also on the oil pan... if you see the pro-comp retrofit oil pan on ebay ... it fits nice but is built for , the fittings leak and the pick up tube that comes with it does not fit without modification. If you Go with fuel injection and use a truck intake it will fit under the hood . You can trim the plastic cover around the throttle body and where it mounts to the intake and have it fit also. It will absoutly not fit in stock form with the transdapt mounts unless you sit it lower in the frame somehow. The seam in the trans tunnel that sticks straight down can be flattened for less headaches later, although it dosent have to be. The stock column shifter will work with some adjustment with a 4l60e but you wont be able to get into 1st with the column shifter. IF you need fuel lines you can pick up the correct size factory plastic lines at the bone yard and buy the fittings at the part store much cheaper and all you need is boiling water to put them together . I pulled the lines out of the wagon i stole the tank out of from front to back and made adjustments where i needed . The harness takes all of 45 mins to strip what crap you dont need out and have a useable harness. MAking gauges and other stuff is slightly more involved but if its a stock engine basically ship the ecm off and have the vats , rear o2's ,and trans if using something ecm controlled taken out and your good to go. I had mine done for 75 bucks a year ago . THer is all kinds of crap rattling around in my head but my wife told me dinner is ready ... So ITS NOM NOM time !

Later guys.
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