Finally getting to it!!! 1970 Duster 340

On your electrical issues, you are more than likely correct that it's a grounding issue. When I do a full bore resto like you have, I always leave the mounting points at the kick panel area mounts for the dash frame bare metal. You may have to skin a little paint off the back side of those places, and also where wiper switches, light switches, and anything of the sort will pick up a ground. Don't forget to make sure the dimmer switch and gauge cluster is getting a good ground also. Maybe you can make some temporary jumper wires with alligator clips on them to trouble shoot. If you can fix poor old sore and painful feet.....I know you can fix this! :D