Right now I'm trying a set of HID's that drop into the square H-4 housings. The light output (4100K) is outstanding. But the bulb doesn't match the reflector very well, so the cutoff isn't very accurate. So I guess you get what you pay for...........
Hopefully someone else doesn't get what you pay for, too. Put those things in projectors, not reflectors.
Yeah man HID bulbs in normal halogen housings is not only ignorant, its just an all around stupid thing to do.
Here is the route I
was going to take, was because other things have come in to the foreground.. and frankly $200+ for two of the four headlights alone..

HOWEVER! that does not keep me from dreaming and wanting to teach others about the awesomeness of proper HID retro's!
http://forums.vwvortex.com/showthread.php?5065880-Today-s-project-bixenon-7-quot-roundsThis is a great thread of a guy who made his own HID lights with products from a very highly regarded supplier of individual projector lenses, bulbs, and ballasts; The Retrofit Source.
http://www.theretrofitsource.com/index.php?cPath=278v
This guy is selling 7" round true bi-xenon headlamps for MB G-Wagens, $430 shipped for a set. The bi-xenon denotes a system that uses only one real HID bulb, and shifts the reflector slightly when switched to hi-beam... no halogen bulbs involved. Nice for early cars and Cabriolets. I'm going to pick up a set of these if I can confirm they will fit into the Vanagon headlight pit, there's not as much room to play with on the vans.
I'm pretty sure the little bulb on the bottom is the city/parking light.
EBAY LINK
I contacted the seller, he said the G-Wagen lights are 8" deep.

I think that's going to rule them out for most VWs.
I just ordered the Ebay cheapo headlight set... I'm going to replicate the build on the Vortex, using the Morimoto D2S projectors, TRS have a complete setup for $300. (and look at the LED light kit, if you spend $300, you get it for free

) I'll post it up when I start the build.
The guy on the vortex used the Morimoto H1's for there projector depth, and only had an inch between plug and stock battery location. I do believe the D2S' are a bit deeper, however I am not %100.
Either way, one day I would love to do this setup! But for now i think I wanna find some Euro-spec mk1 jetta headlights
Yeah, changing it to H1... they are actually slightly deeper, but smaller in all other aspects. What changed my mind is the mount; the H1 has a screw-on adapter for H-4 style bulb mounts...