Bad Ground on my 67 Valiant Dash Cluster?

With the instrument panel dangling from its harness connectors a simple test lamp would show the entire housing as hot. That's the current attempting to use your test lamp as a ground.
If you want/need to continue testing in this manner, get a piece of wire with alligator clips both ends. Attach one end to inst' housing, the other end to bare metal such as column/pedal support and start testing over with your test lamp.
I think I said this before, a permanent dedicated ground wire is recommended.