Bad Ground on my 67 Valiant Dash Cluster?

Yes. I was disconnecting the black wire on the circuit board, and the wrench touched the metal part of the dash. It blew the fusible link under the hood. That seems pretty extreme for disconnecting a dash cluster.

It isn't extreme where a live ALT' amp gauge lives.
Most any service in the manual starts with "Remove negative battery terminal".
The manuals are free downloads too.