For what it's worth; when I started the restoration on my '37 half ton the fuel gauge did not register either. I thought surely it was a bad gauge. In the course of working on the entire fuel system, part of which was removing the tank for inspection and cleaning, I discovered the float (cork) attached to the gas tank sending unit was nearly disintegrated. I also found the related sending unit wiring was in dire need of replacement and contact cleaning. The gauge now works fine and was not the problem, after all.