For the GT? 3.31s are the best followed closely by the 3.15s. Every single test that has been done has backed this up, you do not need a lot of gear because of the way the 6R80 ratios are setup.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.