SVT stands for Special Vehicle Team, theyre Fords elite group of engineers that make the Lightning, SVT Focus, Cobra R, and the "normal" Mustang Cobra. The Mustang GT is your basic Mustang, the least expensive (other than V6). The Bullitt was a special commemorative dedicated to the origianl BUllitt from the movie of the same name. It was limited edition and only came in Highland Green.
Hope this helps.