engine swap

i have an 91 cherokee limited with a 4.0 liter engine that is locked up with auto trans. my question is will any year 4.0 liter engine work? the yards tells me no other 4.0 liter engine will work but did not know why other year engines wont work. please help me with your info thanks in advance!!!!!!!!!

91-95 would be a direct swap. I would swap in you original flexplate or flywheel and distributor. 96-98 should work also. The head would be missing the temp sensor on top. 99+ should also be swappable, but the heads suck. You could swap in the block and have your head rebuilt though. Retain everything electronic related for your year of engine.
Tom

thanks for the info, this will help me out