Looks like I goofed here a bit - I mistook the OPs request for TMCC to be that of a TMCC upgrade and completely missed the fact that this locomotive has an existing LCRU in it! 
Even 3rdRail listed the AC Commander for this specific locomotive further cementing the direction I was heading...
It never crossed my mind that the headlight wasn't AC track powered. I am not sure how any of my LED recommendations would behave on DC; the specs don't list a polarity. I would wager that the base would be -DC and that the tip would be +DC. With the screw base of the original bulb being AC common, and the wire being either the correct or incorrect polarity (based on LCRU behavior), I don't see how a rectifier would help unless you isolate the screw base as well (Maybe my morning coffee hasn't kicked in yet and I'm missing the obvious). I also don't understand the need for a discrete current limiter (resistor) for any of the drop in replacements - that is internal to the unit. @gunrunnerjohn, can you smack me over the head with a 2x4 and set me straight?
