First of all, I'm assuming you're talking about not just the clear halogen headlamps, but the Litronic/Xenon set up, which comes from the factory with a self leveling feature. If your headlamp has an eyeball like projector like the pic of my Litronic headlamp shown below, they are the factory Litronic option. I did such a swap in my car, and even though I did not hook up the self leveling wiring, the headlamps still work normally with the following exceptions:
1) If you don't hook up the self leveling wiring and control box, you will need to manually aim your headlamp beam up, because in the factory set up, the beam is turned down when off, and when you turn on the headlamps, the eyeball beam moves up to the right level after communicating with the sensors. Without the wiring, you won't get any movement of the eyeball, so you have to manually set the beam aim where it will remain fixed.
2) With the wiring, when you turn on your high beams, the high beam will swivel up 2 degrees to help the low beam spread a better beam of light so that you can see further ahead. Without the wiring, you'll still have the low beam and high beam, but without the swivel feature, you won't have as good a light spray when you turn on your high beams.
All the lights (hazards, high beam, parking lights), should work fine by just popping the headlamp in, even without the sensor wiring though.
