Originally Posted by nalc

if you're going to do a retro, save yourself time later on and just make the harness now.

here's a helpful thread
http://www.hidplanet.com/forums/viewtopic.php?t=45050

what you'll want to do is get a pair of relays, one for the high beams, one for the low beams. Run thick 8 or 10 awg wire from the battery through a beefy fuse then through the relays. There's plenty of diagrams in that thread - the only difference will be that you'll be wiring it to your low beam bulb, instead of to a ballast.

the advantage to that is you'll have time to build and test your harness (which is relatively cheap) before going for the retro, and then when you want to retro, you can just use the harness. A few members sell premade ones, and if you know your way around a soldering iron, you can make one.

If anything, I'd suggest doing the opposite - make the low beams yellow, and keep the highs white. yellow is helpful because if it's snowing, it doesn't reflect back into your eyes as much. that's why a lot of cars have yellow fogs. with yellow low beams, theyd be useful in inclement weather. yellow highs, not so much.

Basically, you want thick wiring going to your battery, with a decent fuse. You'll use a relay to switch on the power from that by using your stock headlight switch. The diode and capacitor and multiple relays helps keep the ballast/low beams from turning off if you flash your high beams.