So with the 5A jumper connected to each wire one at a time we get:
Fuel gauge works
Radio works
Heater fan works
Coil shows 12.3V at the positive terminal (grounding the multimeter at the head)
Battery tested as good at O'Reilly's
I don't know about voltage dropping resistors in line anywhere but will go looking for them. I assume that a 1949 truck started life as a 6 volt?
I suppose the next thing to test is the wiring coming from the Ammeter that powers the key switch?
