275/60 drag radial bigger than reg. radial ?

I put a Duster rearend in my 64 Belvedere last night. The wheels I wanna run are 10" wide. They have some MT 275/60 drag radials on them. The total section width is 12". They rub the inside of the quarter panels. My question is....if I put a reg street tire ( BFG, Cooper,General, whatever...) how much less sidewall will there be as compared to the drag radials ? I see the specs for them but none of the specs are for them mounted on a 10" wheel. Thanks for any help

That measurement refers to the section width. In theory a 275 is a 275. In reality, there is slight differences from one manufacturer to another, but not much. My guess is that you wouldn't gain or lose anything.

Put them on am 8" rim, 4.5" backspace