I’m new to this engine swap thing so I hope I can get some help. I was originally gonna do a 5.0 swap but I’m not gonna have the time this summer. I’ve heard 4.0 swaps are pretty easy and cheap. I have a 91 with the 2.9 and I found a 91 4.0 for sale but it doesn’t have the wiring harness. Would I be able to use the wiring harness from the 2.9 or do I have to have to 4.0 harness?

 

No, you would need the 4.0l harness
2.9l used MAP sensor, TFI spark(distributor) and single O2 sensor
4.0l used MAF sensor, EDIS-6 spark(no distributor) and two O2s

Good page to Bookmark here: https://www.therangerstation.com/tec...ry/index.shtml

Look in Engine or Conversion sections for swap info