LOL well an fsm WOULD help, but you have to use what's called critical thinking when working on cars.
I cringe whenever I see someone start a sentence with "I'm thinking it could be....." . That's wrong because you're not thinking, you're guessing. I offered that analogy about working at the dealer, which mostly went over everyone's head, but that's the truth. You can't throw parts at something hoping to get lucky.
The OP, who seems like a nice person, has a bad problem with getting bogged down with trivial issues and avoiding doing the simple stuff. I started losing my patience because everything kept revolving around wiring and voltage drops, and yet not a single meaningful spark test had been performed to establish there was even an ignition problem. If he does a Hemi swap as he speculates doing, he'll think working on this Slant six is a walk in the park, and as prone to be distracted by random issues as he is I fear that'll be another project abandoned midstream.
Moral of the story is diagnose a no-start exactly as the damn FSM tells you to. Check for spark, check for fuel flow to the carb, then go from there. That doesn't mean you wouldn't have a wiring problem somewhere but work your way back to it. People that don't have a clue to begin with are only going to get even more confused when people start shouting ignition switch, bulkhead connector, fusible link. It's beyond me why you would start diagnosing a no-start at the ignition switch when you don't even know for sure there IS an electrical problem yet.
Again: The basic law of owning a Mopar. Carry a known good spare ECU, a known good spare ballast and the tools to replace them. Always.
To the OP...if you don't like the way the wiring harness works, go get one. Go get one. Don't talk and worry about it, go get one. There's always '75 Valiants and Darts always being parted here, somebody for sure has one.
