There is really only one logical option to get HID's on the H2. I searched all over the internet trying to find the right setup and finally did.
This is one of those things that should have been stock. Buy the Sylvania Xenarc X6024 replacement lamps and you won't be sorry. They are very easy to install and not only do you retain low and high beam functions, the low beam HID's stay on when you switch over to high beam.
I ordered my H2 with the wrap-around brush guard (which made installation slightly more difficult) and the factory off-road lights. With the new headlamp assemblies in, you cannot tell that the off-road lights are on as they are drowned in the light produced by the new beams.
You have HID on low beam and maintain the HID's on high beam but there is a second H4 halogen bulb in the sealed beam unit that kicks on and provides more light. I found the lights the cheapest at
http://www.brightheadlights-hid.com/...aled-beams.htm
It's an easy installation and comes with every thing you need. Also you'll find yourself not using the high beams very much afterward because the HID's on low provide great light.