I picked up a new (used) 4.0L yesterday to swap with the current 4.0L in my '99 Cherokee Sport. I noticed the new engine does not have the goofy oil filter assembly (sweet). The filter screws right to the block.

Which years had the assembly? Which years did not? I'll have to go back and check the stamp on the new engine.

 

I dont know about any specific years having that setup, but i do know that some people do it as a mod to keep it from leaking. So maybe the po of your new motor did the mod to that motor.