Also, just to add to Shazaams link posted above, H3 mount HID bulbs ARE available from autolamps-online, with the correct mounting depth.
They also offer their bulbs in a range of colour temperatures from 4300k to over 6000k (very blue). As he says, the bluer the light the less range (penetration) you will get. I therefore always go with the 4300k bulbs.
The guy who runs autolamps used to work for Philips Automotive Lighting devision, so he really knows his stuff. I asked lots of questions prior to buying the first kit. I have no hesitation in recommending them.
Finally, they offer kits that have a single ignotor (as shown in the pics above), or where space is limited can supply kits with split ignotor/ballast wiring. I have always used the single unit versions.
Finally, finally
, duck916's install shows the wiring has been extended between the bulb & ignitor (in order to place the ignitor under the seat).
This is not recommended as the ignitor units generate over 15kv in order to strike the initial arc (running voltage is around 300v). The usual mounting place is to fit the ignitor behind the rad.
Hope that helps,
John.