I wanted to end up with the same width as the 8 1/4 rear ends to get the correct width for the wider brakes. Is 51.4 the stock width for an A body 8 1/4?
51.4 acording to the link posted above
What I do when figuring the axle lenght with
stock bearings:
Get a friend , 2 pieces of wire coat hanger or 2 pieces of lenghts of all thread
stick one in on each side of the housing until it engages the trust block or pins have friend push the pieces of all thread untill the trust is completly taken up on one side and then push back same way mark the allthread from the housing flange measure the travled distance subtract that will put the block in the middle position and allow for the brakes to ride in the drum evenly ,with stockbearings make sure the adjuster is in the middle of its adjustment when you measure the axle lenght you need~
Did I understand the question right..does this make sense?
Add the travled distance than divide