Is this factory 1975 stuff
Gonna pass along something I figured out about wires a long time ago. If everything you need works when you need it to, the engine starts and stops when you tell it to, and nothing bursts into flames or throws sparks at odd times, tape it off to get it out of sight and forget about it...
In my case, 95% of the wiring harness is useless. To do a gen III hemi, you need the start, run, the charging system, and the voltage regulator. So for me, wiring that is sharing the same space, like lights, a windshield wiper system, the blower motor for the heat, or the horn needs to be sorted out, from the live wires for the 1975 throttle sensor, EGR spark advance, A/C system, or whatever the guy before had rigged up.
Than it might be nice to have the warning lights for oil, brakes, and temp. which by the way,, those wires are so long on a slant 6 they actually reach the radiator support.( but these are not necessities, they are luxuries.) It might be nice to have windshield washer, or the stock temp gauge. ( but it's not necessary) But I don't need a 2nd red wire with a fusible link, that's capable of carrying 138 amps to god knows where. I don't need the never ending hub of blue wiring coming straight from the Alternator power, going to accessories that no longer exist. I appreciate the guess work being done in this thread, if only to remind me to be safe. Being told that this red wire maybe somebodies modification has opened my eyes to maybe tracing it to see what's going on in the dash that I may not be aware of. ZKX14 pointed this out, and it's appreciated. We're talking 3 times more amperage than what that system was design for. It only take 1 amp to kill.
I am by no means addressing you, but I've had replies to other threads that simply read, Buy a service manual... It's hard to believe there is an area on F.A.B.O. to post questions, and people actually go out of their way to say, " I don't feel like answering. "Read a book." Maybe those folks should save themselves the effort of typing, and let somebody with a theory, or knowledge take a crack at it. Thank you everybody for trying, and this thread continues...