[Peter Serio]

On 64 or 65 there is no actual ground strap that I can remember, for the gauges ground there is just one thin black wire that is partway tape wrapped into the main dash harness.

One end of that wire slides onto an un-insulated tab that is spot welded into the side of the metal socket that holds the light-bulb for your headlamp high beams on bright red indicator light. (The power + wire that lights up that indicator light-bulb is lime green color.) The other end of the ground wire exits out of the tape wrapping behind the dash bezel and above the clutch and/or brake pedal support. Here is the only drawing I have that shows the ring end attached. You have one sheet metal self tapper screw + a star washer to hold the "ring" end of the ground wire to the side of the pedal support underneath the dash.