You need to git a hold of a wiring diagram it would help, coolermans diagram is of a 1971 should be very similar.
Link
1971 Electrical Harness
look for a single green wire with a yellow stripe is all that is needed the light bulb ts grounded to the dash.
Link
1971 Electrical Harness
look for a single green wire with a yellow stripe is all that is needed the light bulb ts grounded to the dash.