Like GM A-bodies, Fox Mustangs use a triangulated four-link rear suspension. With this arrangement, pinion angle is changed by shortening or lengthening the upper control arms until the angle finder gauge points where you want it. Since the control arms on Project Fox's Competition Engineering suspension have Heim joints at each end with very little freeplay, Bill Buck set the pinion angle at -2 degrees. One caveat on a triangulated four-link is that the upper control arms also locate the rearend from side to side, so the left and right links must measure roughly the same length to properly center the rearend. To adjust pinion angle on a leaf-spring car, shims must be wedged between the leafs and the rearend spring perches.