If you're thinking of putting one in, get yourself a transfercase/bell housing out of a 4.3L 4x4, it'll save you a lot of headaches in the install. The 4.3L gear will bolt right up to any small block chev V8.
a small block Chevy motor will bolt up to any tranny that is behind the 4.3 The only major things to worry about are the motor mounts, exhaust, and a little bit of oil pan work. I don't remember if the 86 is fuel injected or not, but if it is, a TBI 350 will use the same wiring harness and computer. You will just need to get the chips out of the 350 computer.