What was different on the rear, I know about every thing from the backing plates outwards is. Is the axles different widths or the splines on the axles?
I will have to compare the axles a little more closely if you like. The axles appear to be close in specs except the outer axle bearing OD were larger on the LBP axle. The LBP axle also has a 5 bolt retainer compared to the SBP which has 4 bolts.