hey, i"m in the process of pulling the wires from my 2.8 before putting in the 3.1 motor and i was wondering if it is possible to use the 3.1 harness if i use the 3.1 ECM. the main difference that i can see is the junction that goes to the fuses which contains 12 wires in the 2.8 and 15 wires in the 3.1. i am having trouble matching up some of the wires given that there will be 3 extras from the vats or fog lights from the donor car which i do not have on mine. if anyone has tried this would you still happen to know which wires match because the wiring diagrams that i found do not seem to specify where they go after they're inside the firewall short of tracking every wire through the car .

You would just cause yourself much more headache than is necessary. Just swap the shortblock from the 3.1 over, put your 2.8 stuff back on and call it done. That's all you're doing anyways.