i wouldn't have a clue.
i have a bullitt mustang and the only other mustangs i have worked on or been around had different mufflers on it.
maybe someone else can comment on what they sound like on a 3V motor.
Depends on the year. 2005-2009 gt500 mufflers are the same as Automatic GT mufflers. 2010 gt500 mufflers are a good bit louder and have 4 inch thin wall tips and part no. F1 8143 Going off of the part no. You have (f1 7991) you have 2005-2009 mufflers.