1975 Chevy Truck FUEL GAUGE

Electrical problem
1975 Chevy Truck V8 Two Wheel Drive Automatic? Miles

Hi, I've installed two fuel gauges on my '75 Scottsdale and they work fine for a while then the gauge only goes to approximately 3/4 tank when full. We found an exposed area in the wiring where it rubbed against the frame from the sending unit and have repaired that. We still only register around 3/4 tank with the break repaired. Is it possible that the printed circuit board is bad? Would a worn area in the sending unit wire cause the gauge to go south. I plan on checking to make sure we have a good continuity from the sending unit to the gauge. Thanks