Thanks Burd,
The socket is to big to fit in the lighter that you sent the link to - I tried that already.
It is actually the same size as the socket that snaps into the center fuel gauge pod. I snapped both that socket and the fingered socket into the fuel gauge pod, so they both snap into a metal grounded hole that size. I determined the plastic black "fingered" socket was for the pod by looking at posted photos. I have looked at schematics and can't locate the need for the socket in question. The bulb that is in that socket is a newer LED bulb that I put in there to test.
You are correct that all gray wires are associated with interior "dimmable" light circuit controlled by the headlight switch. I believe, making them all related to the dash area.