welcome to the 200+ club mark, it should be noted that you are in the minority, there are only a hand full of people/cars that have gone 200 with a supercharger, I think all together less than 10(?) Im not sure about this someone correct me if Im wrong.
I dont think there has actually been another car except for one or two gt500 that have broken 200 with a supercharger, everything that is running 200+ is either turbo'd(supras) or tt'd!(everything else:lol)
also when those mustangs broke 200 the conditions were optimum, 10+ mile/hr tail wind with cool temps. I remeber everyone(multiple cars that I personally know of) was running 10 miles faster than their previous mile events.