I'm looking to install HIDs on my Mark Lt. Any experience with BiXenon or Dual beam units out there?

I don't know this for sure, but you might be able to buy the 2003-2006 Navigator HID headlamps (the whole assembly) on Ebay and just use those. I know the housing looks pretty much identical on the 03-06 Navi and Mark LT so if there is no difference in the wiring harness it might be a possibility. Please check with the parts department to see if they are interchangeable. For instance there were Navi that had regular headlights and HID, if the wiring is the same and the housing is the same as a Mark LT you can have a stock look for cheap... Hope this helps.

I just got a HID kit from xenonrider.com and put it on my bike.

This guy has pretty good prices too.
http://stores.ebay.com/HID-Outdoor-Equipments_W0QQssPageNameZstrkQ3amefsQ3amesstQQtZk m