I guess you missed my post a little while ago. I did it and it was about $650. Had to do everything custom as the projectors in the housing for the van were not available anywhere. Please only do this upgrade if you use projectors. Installing an arc source bulb in a normal housing will just blind everyone on the road. They should only be used in projector housings with a cutoff shroud. Even normal halogen housings with a glare shield won't cut it in terms of not blinding people.
For the person that spent 4k on an HID upgrade with projectors, they must have gotten the BEST crap available and had like 4-6 lights total. No way i'd spend 4k on something that could get smashed up in a fender bender. It was hard enough spending $650.
Also, in terms of color temperature. If you want more light go with the lower color temp. Having your headlights look blue doesn't get you much and reduces light output, stay at 5000k or lower.
In order to do this mod correctly you will have a modify wiring going to your headlight switch and high beam switch. The plug and play crap that is made doesn't work. The HIDs require power all the time, and the shroud motor requires 12 volts to engage, then when 12 volts drops the spring pulls it back down. The stock setup on the trucks is such that when you pull the high beam lever you lose low beam power for a split second which makes the arc drop. Also, when you push the lever forward it drops low beam power entirely. The bulbs will need a new constant uninterruptible 12 volt supply to stay on constantly. Then you need new wires run to the high beam lever to actuate the high beam shroud. This is all true of the post 1992 anyway, earlier may be a little different with the high beam lever operation i suppose.
All in all, if you do this mod correctly no one will really even know you have HID head lights. Infact the lighting will out perform the stock lighting by a long shot in terms of visibility and in terms of not blinding people.
http://www.oilburners.net/forums/showthread.php?65912-upgraded-headlights-finally&highlight=