The last time I spoke with John Clor this summer (guy who runs <A HREF="www.fordperformancegroup.com">www.fordperformancegroup.com</A> for FoMoCo), he told me that there were about five SVT STA test mules built with the '03-'04 SVT Cobra Terminator engine, and that they were screamin' beasts. John said that all but two were destroyed, so this must be one of them.
The probable reasons for them not being street legal is that concept cars are rarely built with things like mandatory 5mph bumpers, emission controls, and all of the other gov't-mandated stuff.
I"m guessing that it never went into production for the same reason that Ford is killing the Sport Trac & Ranger: It would cut into F150 sales.
However, I see that this one still sold for $57K.