I am sure the leaf springs are a different lenght, that given, I think the wheel base is different. I don't believe the shafts are the same lenght. But there are differences from rearend sizes that play a roll for drive shaft lenght. Like a dana e body has a shorter shaft as with b bodies. Not sure if an 8 1/4 rear would have a different lenght. The ebodies I believe were 46.50 or in that area. I do know you need to make sure the shaft has enough travel as to not bottom out into the trans.
