I don't know about the GTA's but you have to be careful because some mufflers for the GT's position the muffler too close to the rear valance and will melt it.Ninosport says that the GTA mufflers will fit the GT500. Is this true? Anyone running them? I have the GTAs on my '07 GT and am very pleased with the sound. It they'll work on the GT500, I'll go that route.