Thanks for the info. What I will do is pull the 8 1/4 and do a side by side compare. I thought the B housing is about an inch wider than the A 8 3/4. The car is down for the season and who knows if the 2021 will run..
Measuring both would be best, especially since there are several different B-body 8 3/4 widths depending on the year. But the ‘68-70 B is more than an inch per side different, even from an A-body 8 3/4. And the 8.25” is narrower than the A body 8 3/4, not all the A-body rear ends are the same width they changed depending on the style of the rear end.
If you really have a ‘68-70 B 8 3/4 you’ll need close to 6” of backspace with 15x8’s if you want the wheels inside the quarters and not rubbing on anything.
