What do I need and what do I don’t!

[RustyRatRod]

Love to find an example where an ammeter in a '75 actually caused a fire.
I had a '75 4 door Valiant and it did not catch fire. Not even once.
Headlights tripping circuit breaker, yes, and that was pretty much the only electrical problem with it.

If the OP's car has the seatbelt interlock, then there are simpler ways to permanently bypass it.

Or he could just wear the seat belt.

 

[triumphman]

Use these copies for color codes and locations at the firewall connector. They are from a 75 Swinger's factory manual.
If you can locate wiring harnesses out of 73 to 76 "A" bodies . Be sure to check cracks and splices and clean every connector.
Splice with SAME colors.
Good luck