There are two serrated ring terminals, one for the headlight switch and one for the wiper switch. They ground to sheet metal screws to the metal part of the dash. The other ends are connected with spade terminals to the headlight switch and the wiper switch. The headlight ground ring terminal is on the brake pedal mount bracket. There may be additional grounds, like that for other accessories. Just find a good location where a sheet metal screw is into metal dash/body and use that.
Yes, theres 2 serrated ring terminals in harness. I already know of them is for the brake light switch and the other is the instrument panel for wiper and the headlight switch. I have seen that ring terminal screwed to the climate control switch on some cars and mine was unconnected. I will find a location in the metal dash and try to connect it like you said.
