DDMtuning.com. Lifetime warrantied HID kits for <$50 shipped.
Get 4500k 35 watt and call it a day.
DDM does not offer bulb capping (to my knowledge) which is ESSENTIAL if you are going to run HID's in the mustang's halogen housing. The bulb has to be capped to eliminate direct light output straight from the tip of the bulb.
Retrosolutions DOES offer the capping service.
The light goes only to the reflector which is what eliminates the glare typically associated with running HID's in a halogen housing.
HID in a halogen fixture is Bart Simpson
You obviously haven't seen it done right then. it seems like the vast majority of offenders are running 55watt and 6000k or higher bulbs which makes them too bright and too blue.
35 watts and 4300~4500K not only produces a significant amount more light on the road, it adds no offensive glare to oncoming motorists.
2012 GT Premuim - Candy Metallic Red, MT82, Comfort package, Reverse Camera, Brembos and 3.73's.
Mods: JLT oil separator, Koni Sports, Steeda sport springs/HD strut mounts, GT500 Axleback, Air Raid CAI
373 RWHP / 356 TQ - Stock on 87 octane