1970 rr with rallye cluster. One thick red and one thick black wire. I am thinking ammeter.
On my '70 Charger 500, the gray wire with the flat blade connector went to the clock. There may have been another gray wire on a bulb socket, but I can't remember where it went. Maybe left turn indicator?
I have an oil gauge, not a light. That's why. My turn indicator may not be gray, it may be something else. And, I may be blocking - that whole operation was such a pain in the a$$, I just don't want to remember it!