The biggest source of voltage drop in a headlight system is the dimmer switch. It carries the full current draw of the bulbs and it lives in a very hostile environment- - - -under the floorboard. Run some heavy wiring from the battery cable at the starter to the radiator support and use two Bosch type relays to carry the headlight current. Then use the dimmer switch to turn the relays on and off. Be sure to run a heavy ground wire from the core support to the engine block to complete the circuit.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!