1970 Dart matching numbers 340 4 Speed

Couple of suggestions:

1. I would modify the title of the thread, looks like you started an WIW thread or something. Make it more specific.

2. Might try posting the question in the Electrical and Ignition forum - Electrical and Ignition

As to your question:

Not sure if your car is like my 1974, but mine get's power from a lead in the reverse light circuit that heads down to the plug on the transmission. Wire goes through a grommet in the firewall up at the top and is a single wire to the light which is grounded through the dash frame.

Might follow the wire from the light and make sure it passes through the firewall and is plugged into the harness that heads down to the switch on the trans.