My 65 Barracuda's sending unit is not grounded. It works outside of the tank if I attach a ground to the unit and to the body of the car. Then the gauge works according to where i am holding the float. but once it is back in the tank it doesn't work. I am told that it is dangerous to have a gas tank that is not grounded. suggestions? thanks.

Luke

Ground the sending unit.
The factory used a metal strap that clipped onto the fuel line and to the hard line going into the sending unit. This strap bridged the "ground gap" over the small section of rubber hose connecting the two. Look at some wrecking yard cars for the strap.

Note that even if you ground the fuel tank, the sender will not be grounded because of the rubber gasket, fuel "sock" and rubber connecting hose keep the sender isolated from the chassis ground.
DD