They produce a "white" beam. 3600K
http://www.piaa.com/Bulbs/BulbsAbout.html
http://www.hirheadlights.com/stats.htm
Yes, some modification is req. It can be done with a good knife, file, or Dremel tool. The guy I got mine from trimmed them before shipping on one set, not on another.
At the end of the day- it is a regular filament, with an Infra red coating, and round bulb to maximize IR reflection. The coating reflects IR (non visible) light/energy back into the filament so it "burns" brighter in the visable spectrum.