Flowmaster's are done to death. It's like the most common thing ever on a Mustang. IMO, they don't have that muscle car sound. Not like a Cherry Bomb anyways..
My point was that having an old car that made some noise wouldn't really throw away the "sleeper" image because everyone expects everything with a V8 to have flowmasters on it. NOT that you should run flowmasters. At this point, there are almost none of these cars left "in the wild". The only reason you'd ever see one on the road is because someone did the work to put it there. Anyone who would race is a car guy, and would know that.