66 Dart gas Gauge

Loose or broken pins at those inline harness connectors are too common, especially the ones near top of board. I wont say you should add solder at the pin to board connections but a little dielectric grease and be very careful with them is said.
I couldn't stop short of new limiter or solid state regulator, and all new light bulbs and sockets while I'm there. I've lived the "one problem after another" period and became quite proficient in inst' panel R&R. I learned, clean every electrical contact point, add dedicated chassis ground wire, bypass amp gauge, covert it to volts gauge where possible, everything i can do to prevent repeating inst' panel R&R.
Resealing wiper pivots is a totally different service and thread topic but is relevant. Working through the dash is much easier than working under it.