Don't forget that you can bypass certain components like the dimmer and just touch/connect the wires together for high beam and test. Everything you buy anywhere, including NAPA is Chinese or Mexico. If the HLS is old, clean the thermal contacts. The best HLS would be a good original donor or NOS. Not too much to go bad on them....or
this
There is NO headlight relay on a 1960. The only relay is the horn relay. That is what the supplied relay is for. Do not use a relay in the headlight circuit.
There is one wire from the headlight switch to dimmer input terminal. Then a wire from low beam terminal on dimmer to all low beam contacts on bulb connectors. And a wire from dimmer high beam terminal to all high beam contacts on the bulb connectors.
Each bulb connector has a ground wire to be grounded.
It does not matter which terminal on the dimmer is used for High and which for Low beam, just so the high and low wires connect to bulb connector properly. See manual electrical section/wiring diagram TPM-6750-1.