Do your research and make sure you get the correct frame mounts and the proper crossmember. As far as mounts go, the LT1 is just another SBC. I think the 4L60E is just an electronically controlled 700R4. Get the right mounts and crossmember and your *swap* is now just an * engine replacement*. Determine what EFI harness you're going to use. I like the harness I got from Howell but a lot of guys are using Painless. I've heard both good and bad about them but I've never used one. There are other harness companies, too. Determine where your fuel line will need to be routed. RUN NEW FUEL LINES!!! When I first did my TPI swap I tried using my old 5/16" main for my return. It was blocked and wouldn't let the fuel press drop below 100 PSI !!! Replace all 3 of the lines. Main 3/8", return 5/16", and vent 1/4". Wiring for alt, starter, a/c, etc may need lengthened/shortened. Headers and exhaust are the same as any other SBC. Driveshaft will probably need to be shortened but I couldn't begin to tell you a length. When you get the cash, drop in a 3.42/3.73 rear gear for that 4L60E. If you can pull and replace an engine whether it be a SBC or SBO, you can do this swap yourself. With a good EFI harness, it'll be plug-n-play. Only one sensor each plug will go into. Lay out the harness on the floor and identify each plug for each sensor. Do this a couple times and when it comes time to install in the car, you'll know where everything goes. Believe me, if you have enough knowledge to R&R an engine, you can do this yourself. I did mine and I'm no ace mechanic. I swapped my 84 Cutlass from a V6 3.8L Buick to a 383 TPI and T56 6-speed. If you need help, there's enough of us here who can either give you an answer or we can lead you to the people who can answer your questions.
Will it be worth the time and trouble? YES!!!
Will it make a fun ride? ABSOLUTELY!!!!!
Will it get better fuel mileage? Probably
Will it have better drivablity? Most definitely!!!
Will the "Pride in your Ride" increase? No Doubt !!!
The ability to say "I did it myself..."? Priceless!!!
So, go out and pull that hood off and get that old engine out... It won't happen over the course of a weekend as there are a lot of little things to get done. Just break everything down into small tasks and you'll eventually get it all done.
Tada! Your *swap* is now in the car and running. And yes, that smile on your face is a normal side effect...