Unless you have reason to think the axle ratio was changed after the car left the factory, check the label on the door jamb, assuming the label is still there. I don't have '06 information, but I am not aware of changes in coding between '06 and the '07 information I have. CG is 3.31 with limited slip.
2007 Mustang GT Coupe Premium
High Performance White
/Dark Charcoal Leather
Rear Spoiler Delete
Interior Sport Appearance Package
MGW EJECT Power Point Plug
If you pursue perfection, you will never attain your goal. You may, however, achieve excellence. Takata has a long way to go.