Differences between 455s

[-83MONTESS-]

the 500 caddy is actually lighter than any other GM big block, so dont count it out for that reason.

I believe the Olds is lighter than the caddy. The Caddy is around 625 and the Olds is around 615-620 IIRC

 

[hotwheelsboy28]

I have a 1980 Buick LeSabre Coupe and was juggling the same question for a couple years. My car was a 4.1 L V6 from the factory and over the years has had a Chevy 327, 350 and an Olds 307 in it. Finally one day I decided it's time to tool on the old Buick, I found a 90,000 orig mi 1973 455 Olds on craigslist for $300.00 so I ended up with it always wanted a big block in it. It was in great shape only had to polish the crank and hone the cylinders, then the journey began how much do I want to do and spend on it? Well i'm not rich so I went moderate, refurbished stock short block, had the heads worked with all new valves,new Comp Cams Extreme Energy .486/.488 lift cam and valvetrain with screw in studs 3/8 pushrods and guideplates with the excepion of 1.6 Scorpion roller rockers, Edelbrock Performer intake, rebuilt Quadrajet the orig one to the engine and Flotech headers for a 70' hurst Olds. Then the hard stuff what will fit off the 307 that I want to swap and or reuse? After many hours of swapping parts and fab work here's what I came up with to save cash and weight, Alum intake for a 455,(these parts were off of the 307) starter, short "pancake"ac compressor (modify the brackets to make it work) reused the alternator,new power steering pump,all the pulleys. The water pump ,fuel pump,starter,flexplate,valve covers, with adjustable valvetrain I had to order 3/4 valve cover spacers also,oil filter and distributer fit both engines 307 and 455. Even the frame mounts lined right up.The belts were a little tricky trial and error. My car is a B body and probably has a bit more room than a G body under the hood, but still it was a tight fit here are some pics, the color is AMC blue.
I just finished the fab work on my crossmember to just test fit it, well to my surprise it fit perfectly, my old one (the painted one) had clearance issues it was stock with a short 350 turbo, I put in a long 400 turbo that was the orig one behind the 455.I have almost $4000.00 invested in motor, drive shaft, and crossmember and transmission at this point.Me my friend and my brother done all the work, and i done all fab work except for the d shaft and trans rebuild. Hope I helped and gave some insight to your decision,Jon.