You'll need custom engine and transmission mounts. Series 1 engines differ greatly from Series 2 and 3 engines, so not all conversion mounts sold that work with Series 2 and 3 engines will work with a Series 1. Some might, however.
You'll need to build/assemble your own custom CV axles to use with the 4T60-E. See my webpage on the subject here: http://www.gmtuners.com/swap/axles.htm
(make sure you read the DISCLAIMER at the top).
You'll need the properly matched model year Series 1 PCM to run everything, and a wiring harness to match. I have wiring instructions on my website that you can use to build your own or you can try to find someone on here to make you one.