I'm not sure about how difficult this would be, although among other
things you would need to transplant the computer and wiring harness
along with the engine.

Another thing to consider: Are you going to have issues with your state
and emissions testing? I live in Illinois. I had a 1985 S-10, and put an
305 out of an 1987 IROC. That was putting a newer engine in, so that was
 no problem. Putting an older engine in would definitely be a problem
where I live.

On a side note, my buddy who helped with this engine transplant never
got things working properly, so he had to take off the tuned port fuel
injection and put a carbuerator on it. Since the original engine was
carbuerated, this would probably fly with state emissions testing. 4
cylinders is less than 8, and potentially less complicated, but by no
means easy in regards to engine computer transplants.

Sean