Ive got a 96 f150 2wd 5 speed, and an 85 f150 which is a 4wd 4 speed. the 96 is in great shape, runs like a champ, and the 85 has way too may engine problems but the transmission and 4wd works just fine. How hard would it be to peel the 4wd stuff off the 85 and install it on the 96? how compatible are the two?

 

Much easier to pull the drivetrain out the 96 and put in the 85

 

Transmissions are not compatible with the opposite trucks.

 

You'll have to use the transmission and transfer case as well as the complete front end. You'll end up with a 4 speed '96 F-150 which probably won't command a ton of resale but if you don't care, I say do it.
It's all bolt in stuff, just make sure the gear ratios are the same in the diff's.
This was a 2wd.....