I haven't seen a Mustang rear with the upper control arm perches on them from the factory. An 8.8 is essentially a 12 bolt in comparison, depending on the spline Most Mustangs have 28 spline axles, the Hi Po Mustangs and Explorers have 31 splines, and the stock 12 bolt is 30 spline. Also you have the c clips on the axles for both the 12 bolt and the 8.8.