I ran halogens for years in my 59 Suburban (4 headlights when high beams are on) without relays using the stock headlight switch. Current draw from halogens is a tad more because of wattage. If you are worried about it, run a relay with 10 ga wire up close to your headlights, activating it with the headlight switch. That takes most of the draw off the switch and gives you less voltage drop right at the headlights. That means brighter lights, at least in theory and according to everything you read on the interweb!
