I HAD 275x60 mounted on a 7" wheel on the rear of my '67 Plymouth. It's TIGHT and requires extra work to change. I had to unbolt the shocks so the rear housing could drop low enough to get the tire up in the wheel well. Also, a 275x60 is really too big for a 7" rim, 255x60 is the largest recommended.
I went from 275-7" rear/245-7" front, to 255-7" rear/ 235 on 6.5" front. I can now change tires without the big hassle.
BTW, most of the aftermarket cop wheels do have 4.5" BS but all OEM 7" & 8" wheels are 4.25" BS.