Small bolt pattern 8.25

^^^^^^ what he said^^^^^^^^
I learned that in 1971/72 when I stuffed G60-14s into the stock tubs of my 70Swinger, and custom-built slapper bars; and instantly started stomping all other stock small-block comers, lol, with a totally stock 340. And some hopped-up ones too...... Yee-Haw.
Man that pissed off a lotta my high-school classmates.
Next stop; 4.10s
I was 18 and on the top of the World!
I have a 68 Barracuda now, and have been able to stuff 325/50-15 BFG, Drag-Radials (on 10s) into the stock tubs , and the car is slightly lowered. As long as I take it easy on the turns, I mean drive normally, I won't get any rubbing. BUT, For anything goes, I have a set of 295/50-15s also on 10s.
I only had to move the springs over, and I narrowed the rear end to be able to use a 4.5backspace; which is a common size for 10s

Ima thinking the 72 Duster has the same or similar tubs.