What all is needed/necessary to swap an AX-15 transmission into 1988 MJ manual 4.0 vehicle? if this has already been covered can it!

 

If it started with the AW4 automatic, you'll need to swap the transfer case as well. The 88 AW4 had a different spline count. It's also about an inch longer when you're looking at driveshaft lengths. Personally, I would not put in a used AX15 in unless it was either very low mileage or rebuilt with new synchros.

 

Seconded ^

I swapped a '98 AX15 into my AW4 2000 XJ.
The main variations that come to mind through the years:

Transfer Case - spline length and count varied through the years so this is important to match up.
Pilot Bearing - depending on the engine/trans and model years make sure the right Pilot Bearing is sourced.

Is it a manual to manual? (Getting rid of a stock Peugeot or AX5) or is it an auto to manual swap?
Auto to manual could require: driveshafts, pedal assembly, PCM, etc. Lot's more parts needed.