The 8 1/4 thread

so if a person has a 8.25 rear end ( 27 spline/pre 1997) and the carrier has a 2.45 higher gear ratio it will accept a higher gear ratio or even a whole new/different carrier/ring and pinion as long as its 27 spline with 2.45 or higher gear ratio. might just have to change the carrier bearing and deal with a tone/reluctor ring.

All i did with mine is change carrier bearing and it fit with no issues.