Wow
a lot of tailchasing and guessing in this old thread! Fact is, the headlamp switch is the same whether you have a car that turns off the parking lamps when the headlamps come on (all cars through '68 except Barracudas) or a car that leaves the park lamps on with the headlamps ('69-up). It's safer to have the parkers on when the headlamps are on; that way if a headlight burns out other drivers still see you as a double-track vehicle (not a motorcycle). You don't need a relay and you will not overload the switch by making the easy mod to keep the parkers on with the headlamps.
Remove the headlamp switch and place a short 18ga jumper between the "P" and "R" terminals on the headlamp switch body, right down at the base of those terminals. Make sure the ends of the jumper are neatly tucked so they won't touch any adjacent terminals, then push the connector block onto the switch, on top of your new jumper wire. That's all you have to do. It puts the tail and park lamp contacts on the headlamp switch in common with each other. '69-up cars fed the parkers and tails from what had previously fed only the taillamps (which obviously remain lit with the headlamps).
