Gas gauge off by 1/4

The factory service manual shows the sending unit being accessible on the front side of the tank (pointing toward the passenger seat / trans.housing). The sending unit screws in on the passenger side, front facing curved area, close to the passenger-side, rear wheelwell.

Since the sending unit is located on the forward facing (toward the transmission) gas tank panel (not the top of the tank), you do not need to remove the tank to gain access to the sending unit area.

You should be able to disconnect the fuel lines and the wires at that panel point, then simply un-screw the sending unit, and remove/replace.

Someone that has a factory shop manual might be able to post a factory drawing of the location of the A body gas tank and the location of the sending unit.