According to Rob, the next crucial modification was changing the ring and pinion. He swapped out the factory gears for a set of Ford Racing 4.10s. "They're so much better. The cars should have come from the factory with them." Ford engineers would probably agree, but CAFÉ standards dictate a ratio that is more miles-per-gallon friendly. Mod motors like to rev, and centrifugal superchargers make their power up high, so the steeper gears are a better match for this engine's powerband.