I'm doing the same only into a second gen,  and my truck is a 85 fuel injected.
should bolt in. just remember the block and head are different than the early ones
so when you get parts you need to remember.

i think also the oil pans are different but i hope it does not matter.  i hope going from 4x4 to 2wd wont work but going from 2wd to 4x4 straight axle will have enough clearance for the sump and pickup.  cool  i am stalling on my project! let me know when you are done you can do mine lol!