I have also seen that Saleen sells an HID upgrade for about $899 for the new Ford Mustangs.
They are a 7" unit, but they are not sealed....I don't know if that is something that can be modified by putting a lense cover on the front.
I was trying to figure out if it could work...any one know anything about non sealed units and if they can be modified to work?
http://www.saleen.com/hid.htm
the actual light fixture and housing are separate pieces, so only the 7" unit will be used.