I purchased these gears and had Mustang Magic install them. I went w/ 3.73's because at the time the car was still a daily driver. Looking back on it I definitely could have went 4.10's, but I'm very happy w/ the 3.73's. FRPP makes good stuff, and these gears are definitely worth it and high quality. Mustang Magic installed them in under 2 hours with ZERO whine or noise coming from them.