instrument cluster ground

Also, there's a "trick" to dash lights.

The dash dimmer control gets power TO it from the tail fuse, goes through the dimmer, then goes out of the dimmer TO the instrument fuse. This is the small fuse on one end of your fuse panel marked "inst." Turn the switch to either "park" or "head," make sure the dimmer control is "turned up" and also wiggle it to be sure. The fuse should have power on both sides of the fuse.

Does ANY dash lamp, IE heater, radio, etc, work?

Yep, not that I know/understand everything you said Del, but I meant to mention the headlight switch is cheap and can be had from a jobber for around $15