I am rebuilding the front axle on my 1950 3100, and I ran into an issue on the spindles. I am using spindles from a 1954 3100, and the upper bolts holes where the backing plate mounts to the spindle are a different size than the 1950. The spindles from the '50 have larger upper holes on the spindle (7/16"), while the '54 spindles have (5/16" I think). Why the difference?