It is an FSX compatible skin created to be used with the FS2004 US-2B Bicentennial Tracker model ONLY!!
Available HERE.
It will not work on the original US-2A model, as that model has a texture mapping issue on the right engine nacelle.
Unfortunately, as noted, it's an FS2004 model, and therefore the _spec and _bump textures don't work (yet), and I couldn't make it glossy as the alpha channel is set up for transparency and not reflection. But, hey, it's not so bad in flat paint.

Enjoy!