Interesting. Looking at the 2 of them they are almost a perfect one for one on the ecu. If the current harness was long enough you could use it and only have to add 6 wires. The O2 sensor at pin 23, The injectors at pins 17, 18, 38, and 58, and the starter relay(Not sure about the starter setup. If you go the other way and use the truck harness you need to see what you can do to preserve the engine harness connections to the body that go to power/ground from the YJ harness to the PDC and bulkhead to the cluster. That would be 3, 4, 5, 8, 9, 11, 12, 25, 29, 32, 43, 47, and 57. All these wires currently at the ecu in your old harness and are needed to interface to the exact same pins on the truck ecu harness. The other wires on the new harness should just connect up to the sensors on the engine. I am not sure about placement of the new ecu but if it is close to where the original ecu sits then you might be able to do this easy by taking the back shell of the connectors off and just pull the pins out of the old connector and put them in the new one. I will have to look at the starter relay to figure out the differences there.