might want to consider your speed at rpm. with my galaxie when it had 3.00 or so flat in the rear the t5 would have made the car do 100 at 2500 rpm or something like that. needless to say I went with 4.11 gears. id go at least 3.73 with your rear depending on your tire size and possibly 3.55 if you drive a lot of interstate.
this speed calculator should really help you determine your rear gears.
Ford Mustang: Mustang Tech: Calculators & Decoders: RPM Calculator
this speed calculator should really help you determine your rear gears.
Ford Mustang: Mustang Tech: Calculators & Decoders: RPM Calculator