71 Duster rear tire size

I have 15x10" ProStars with 4.5" with 295/50R-15" tires on the rear of my Dart Sport. They fit without the offset shackles even. I have about 1/2"-3/4" clearence to the springs. The tires are close to the outside lip but with an 8" wheel a 275/60R-15 should fit good.