Headlight switch is grounding 12v to body

Hey guys im new to the forum, ive read many threads on headlight issues and dimmer switch problems and i have checked those components already.

The car is a 1971 Demon sizzler with a 340 swapped in, 4 speed as well.

Ive been putting together a rallye dash and ive purchased new harnesses from year one already. The only harness I haven’t changed was the tail light harness. Figured it should be plug and play but alas nothing ever is. All the lights were working a couple months ago but now i have no dash, headlights, marker lights, or tail lights. When i use my power probe on the car with the key off and headlight switch on, the body of the car is reading 12.5v! Also ive noticed with the headlight harness plugged in with the key in acc. or run it also reads 12.5v. Ive pulled the entire harness back out of the car and cant see anything wrong with it. Any advice?