Ford Racing shows a different part number for the 2015 gears. The only ratio's that they show at this time is 3.55 and 3.73. Neither is available as of this time and my back order list shows an available date of 1-15-15.
The following is their description:
- Fits 2015 Mustang GT 8.8-inch IRS center section
- Requires M-4210-B3 2015 Mustang GT 8.8-inch ring-gear and pinion install kit
- Made in United States in Ford's Sterling Axle Plant
- OEM Quality - our superior surface finish, hardening and manufacturing consistency provide the strongest and quietest gears in the market.
Roland