I have a '55 ford F-100 that has a donor 9" rear diff that didn't have an ID tag. I think I narrowed it down to a '77 Bronco but not sure. Replaced the ring/pinion. Had to do brakes so decided to do bearings and seals. When I did the bearings I noticed a small gouge in the drivers side axle at the seal race. I used emery paper to smooth it out but it didn't hold and the seal on that side is leaking. Tracking down a new axle shaft is crazy unless you get a "cut to fit". Here's what I know - The old shaft is a 28 spline, with 5.5 stud pattern, it had ball bearings so I think it's a "small bearing" set? and the shaft is 29 7/8" long from axle face to tip of splines. As long as I'm asking can a "big" and "small" bearing set be swapped out? Has anyone used the cut to fit and how did it work out?

 

You can get the correct axle from anyone of many aftermarket axle companies using the measurements you just gave here. The axle bearing has to fit both the axle housing (outer diameter) and the axle (inner diameter)