I know the 9" is stronger and I don't believe any other rear ends have that pinion support bearing, but what I don't understand is why would anybody put a 8 3/4 in a 9" housing ? If you are going to have a ford 9" housing ford brakes why not just use a 9" center. It just makes no sense to me. I think the guys at Moser are morons for doing that.
