Just plugging in halogens "should" work ... but beware of electrical gremlins!
Several years ago I switched from sealed beams to halogens in one of my trucks ... and the results were completely unpredictable. I was never sure what would light up and what wouldn't. As you can imagine, hitting the dimmer switch was a real adventure. None of the guys in the shop - not even the shop foreman - could figure out what was going on. (I was turning wrenches professionally at the time.) After trying everything we could think of, I finally switched back to the sealed beams.
