Speaking from the perspective of an old dirt track racer who used a lot of those HO72 4.10 gearsets back in the late 1970's (one reason they're so scarce now), the ring gear carrier has a different side spacing, so it must be changed along with the ring and pinion. If you can find the Detroit Locker center section as well as the gears, grab that, too. They're a little noisy in turns, but in a slippery situation, the pulling power is awesome.
Jerry
