72 duster firewall wiring questions ???

BTW, make sure each of your wires that are soldered are well supported a few inches from the solder joint. The reason is that solder will wick into the wire strands and create a 'hard spot' in the wire just outside the connector into which they are soldered. This hard spot is where any bending force on the wire due to vibration will concentrate and can work harden the soldered wire just outside the connector, and eventually break it with the regular vibration of car operation. (This is from direct experience in a race car.)

Glad your brown wire voltage is solid now; that is good for the future of your car.