Corky,
Reading zero on the gage indicates an open circuit. Remove the access plate and unplug the connector.
Ground the white wire that connects to the main harness. (Be carefull - the pink wire from the main harness is hot.)
With the ignition switch on, the gage should go to full.
If the gage is uneffected, check the plug at the driver's side of the dash, where the dash harness connects to the rear harness. The other possibilities are a incorrect connection at the gage, or a bad gage.
If the gage goes to full, try connecting the pink wire from the tank to the white wire of the harness. Maybe soneone used the wrong wire to connect to the sender. If you still have the pin extractor tool, you can reverse the plug wires, avoiding
removing the tank...