How hard would it be to find a rear end with the sbp?
Just about every 6 cyl A body made before 72 had SBP 7.25 rears. I scrap 3 or 4 a year. I'll have one here in Savannah soon. Count the bolts on the cover of your rear . if there are 9 you have a 7.25. If there are 10 it's an 8.25. As has been said, I wouldn't swap an 8.25 for a 7.25, but if you're running one already, it's a bolt in swap.