engine swap

I want to put a 1991 22re into 1994 pickup which also has a 22re motor. THe 1991 truck was 2wd and the 1994 truck is 4wd. What problems am i going to have or is it going to be a direct bolt in? Is there going to be any problems using the exsisting 1994 computer or will have to swap it out with the 1991 computer?
Anything else i am missing?

Thanks for you help,
Jay

Pretty much a direct bolt-in. There may be slight differences in emissions sensors, etc between the years. Mark all the wires and hoses on both first so you know where each goes and what it's for.