Parking light grounding

[Joyridin]

My 68 C10 seems to have a bit of a ground issue I believe. When I turn on the parking lights, both turn signal lights light up (not full brightness), and the turn signals stop working. When the parking lights are off, the turn signals seem to work as normal.

Somebody chopped a bit of the wiring for the front parking lights years ago. I assume that one of the wires going to the light is for the parking lights, one is for the turn signal, and the housing is the ground? Is this correct? If not, does anybody know where the actual ground wire for the front parking/turn signals are located?

Thanks.