I was wondering if the swap for the stock exhaust was straight forward with the GTA's? I heard that sometime during the mid-production run on 2007 Mustangs, Ford realized that they were loosing money on the intricate metal/rubber exhaust hanger they designed for the 2005+ Mustangs. Thus they switched over to a cheaper rubber only hanger system to attach the factory exhaust. Unfortunately, this system will ONLY work with factory exhaust and will not allow for installation of aftermarket exhaust.
I can't see any problem but if you are that concerned about it Brenspeed sells a stainless steel hanger kit for like 45 bucks if you want to replace the rubber ones.