is this the harness you have
https://www.psiconversion.com/instru...structions.pdf
If so, what I said in my earlier post is correct. That small red wire energizes one of those realays, which then powers all stuff on the engine that needs switched 12V, coils, injectors, O2 heaters, ECM, TAC module and a few other things. The two large black wires that are down by the crank sensor go to the large battery post.
If you still have it, the coil/distributor wire works well for triggering the switched 12V relay.