i need to dump the v6 in the 85 cherokee and have a 4.0 and tranny from a 88 but not sure about the swap..any pros or cons on this subject will help me .
thanks much.

Its a lot of work, and you need many more parts other than the engine and trans.
You need the transfer case, tranasmission shift linkage, front and rear drive shafts, exhaust system, fuel pump and fuel lines, engine mounts, radiator and radiator support, wiring harness, including ECM, all fuel injection hardware

Oh and a BFH (big f...... hammer) to massage the firewall so the engine will fit.

It might be possible to do if you had a 4 liter jeep to supply all parts and give you a guide for how it goes together,

Otherwise, it becomes very difficult. The '88 engine you have is pretty old. How do you know it has much life left?

4 liter jeeps are cheep. You might be better off to sell what you have and buy one.

Or modify your 2.8. I did on mine and it was very successful. PM me if you want the details.