What must you change in order to do a motor swap from the 2.5 motor to the 4.0 in a 1998 Jeep Wrangler TJ?

The only way this monetarily makes sense is to have a donor vehicle. You will need to swap not only the engine but many, many other parts. Without a donor vehicle, I would forget this and sell the Jeep you now have and purchase one with a 4.0 The aforementioned is absolutely correct. I am in the midst of this task and I have labored many....hours and the main issue is the wiring harness. Granted, I did the conversion from a 1991 2.5L to a 1994 4.0L.. You must weld new motor mounts..new emissions(depending on where you live) and the WIRING HARNESS..what a pain in the...you know..new computer, new driveshaft (maybe)..and the list goes on