Disconnect the lead to the sender on the back of the gauge, Turn on the key. If the gauge pegs to Full, you have a good gauge and good gauge ground; otherwise, the problem is in the lead to the sender, the ground at the sender, or the sender itself.

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.