I'm not sure how much interest there is on here because most of us have v8s. For those that have 258s that they want to convert to 4.0 FI or want to swap in 4.0 motors,
I have started making conversion harnesses for people on the CJ forums. Basically all I am doing is taking a 91-95 Cherokee or YJ donor harness and removing all the wires that are not needed or used in the conversion to clean up the harness. I label everything you need to splice into and test all the wire connections for the ECM and connectors to make sure they do not need to be repaired. Then I also use the left over relays to add the headlamp switch bypass through the PDC so your fuse and relays are cleanly inside the box.
I also add an SI style alternator plug so that you can run the charging system through the PDC. The PDC has 2 maxi 60A (120A system capacity) fuses to protect the charging circuit. This eliminates the need for the fusible link wire which can be a pain in the rear to replace if it busts, this allows you to just simply pull and replace the fuse once you fix the problem.
There are several unused power wires in the PDC for items like heated rear window and accessory circuits that can be repurposed for the accessory circuits in wagoneers with electric seats and other items that draw their juice from the solenoid on the fender well. Just depends on what you need if you want a harness.
If you are using a starter with the solenoid built into it, the PDC also has a starter relay in it with a nuetral safety switch wire that can be grounded or spliced into your tranny harness. This would allow you to completely eliminate the fender solenoid and clean up the clutter under the hood.
The overall idea of this is to provide a harness that is much less the cost of the store bought conversion harnesses and looks clean. All that would need to be done is to remove anything not needed from the original harness and leave only stuff that is critical(ie oil pressure sending unit, temp sending unit, ac, blower motor, etc.) run that into the loom and then cover it all up. It will look like one harness instead of two.
Here are pics of the first one I did, as I build more I'll try to get better pictures.
Cherokee harness pulled from a 91 donor
All the extra wire removed and everything labeled
All the wires that came out of the harness
Prices are 150 plus shipping if you pull a usable harness and send it to me. 250 plus shipping if I have to acquire the donor harness from a part out and send it out. I'm only going to do these one at a time with payment due only after I have finished the harness and its ready to send back to the buyer.
I am willing to do obd2 harnesses but the prices will be higher due to the added complexity.