First time MJ buyer
 

Well I've got an XJ and ZJ, now I found a $500 MJ. It's an 88 sportruck 2wd with what I believe is the 2.5L and 5 speed. Question is, I'd like to convert to 4x4 and use XJ parts, what would I need to do to the rear axle to use an XJ axle? I know the springs are under the axle on the MJ.. I'd like to swap a 4.0 and AW4 from a 96 XJ in it, but I'm basically looking for any tips or things to look out for, thanks guys!

Spring perches are setup at different widths. So even if you wanted to run SOA, you would need to cut and have new perches welded on. That said, SOA typically nets 5"+. IMO, it rides better SUA.
Since its 87-up, the engine bay will fit the 4.0L just fine. If you do not have emissions testing Then using all the the electronics will be the simplest method when doing the later-model 4.0 swap. OR, even if you have emissions testing, a smog ref can certify your swap.
Dash is basically the same, but with the newer harness and such, you will need to use the all electric later model IPC.

Welcome to the MJ side of jeep ownership

From the doors forward a mj and xj are twins,From the doors back things are different.On the rear axle swap it will take cutting off the spring perches and welding on new ones.But like said going spring over will give you a good lift for free.