There is supposed to be a newly engineered common rail fuel system conversion coming out for the 7.3 to replace the heui, at least that is what David Lott was discussing briefly. We haven't heard much of anything since.
A lot of the trucks built for big horsepower still seem to be pretty streetable. There are valet switches for the 12v's to cut fuel delivery and we all know the electronic engines can be "turned down" with ease in most cases.