Hum, no that's not it, I made a eeply to this very post and it's gone,
I will try to remember the gist of it,
My 81 for example jumps the the headlight wires from the drivers side plug over to the passenger side, I had to rewire my headlight plugs for the square headlights since my car is custom, anyway, I found the connectors very worn within the headlamp plugs and they did not make good contact until tweaked with needle noses,

also not for the purists but the juice for the headlights which are high draw run thru the switch then out to the headlights wiring people like MAD make kits to add relays out at the lights, so you get more juice to the light hence brighter lights.

Cheers, T
Hope this posts this time :)