Fuel gauge not working. Have a 71 chevy nova, fuel gauge is stuck past full, when I ground out sending unit wire at the gauge it goes to empty, unhook ground jumper it goes back to full, same thing when I ground the connector in the trunk, it goes to empty then back to full when remove jumper wire to ground. Does that mean the gauge is good and the wiring is good - al least back as far as the connector in the trunk - and the cause is most likely the sending unit in tank ? Any ideas ?

Sounds like a sending unit problem.

Are there any other / further tests that can be performed to make sure of the problem ?

There may be resistance tests, if you could get your hands on a shop manual or Haynes Manual.

This may help,

https://www.bing.com/videos/search?q=how+to+test+a+fuel+sending+unit&FORM=VIRE4#view=detail&mid=7E8F4D4808EEC9FD0FA87E8F4D4808EEC9FD0FA8

Yeah, good info but look like I need to take unit out of tank and drop tank to do it, what I was hoping to avoid - oh well, that the way it goes I guess. Thanks everyone