Dan what year truck ? If its a 46 this may not help you...

On my 54 the harness has two black wires, one goes to the gas gauge and the other to the gas tank...

The Assembly Manual Sec 12/12.00 & 12.01 shows the wiring for the gauges...

This is how my gauge looks...


1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years

Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974