I was at a S&S last night and a guy had an '05GT with GT500 sidestripes, Shelby lettering, and Cobra emblems and was trying to sell (the car was for sale) it as a GT500. He hadn't changed any panels and had the hood up - no S/C. A few of us asked him about it obviously not being a GT500 and he said it was his wife's "chick" GT500 and then wouldn't answer any more questions.
My car is an '07 GT with lots of mods including a S/C and I would NEVER consider trying to rebadge it or call it anything other than it is - an '07 GT. I prefer to let the performance speak for itself.