Here is my latest HID retrofit. I'm using a pair of Acura TL Bi Xenon projectors, mounted inside the Z headlight can.
As you can see, this pair is a lot more compact, and took only minimum trimming of the headlight can, compared to the BMW projectors pictured in the above posts.
I bought a pair of spun alum headlight covers, had them powder coated black, then had a 3" hole bore in the center, for the projector lens to protrude. I also bought a clear plastic headlight rock guard cover set from Black Dragon, to install over the finished headlight to protect against pebbles/bugs etc.
I'll take some pics once I get a chance to pull the ones in the car now, and replace them with these...
click-em