Unless this was added in later years, there is no ground from the cluster to the column. IT IS a good idea to add one. The clusters were traditionally grounded through the mounting screws......a poor design.
The light switch is not in the dash, just resting under the dash, does it need to be in the dash to ground it? 67dart273 mentioned a voltage limiter inside the fuel gauge and the black cap on the one stud,
sorry I not sure what to look for. There is 12 volts going to the to amp wires.
