Rear tires- 225-60-15 on 4-1/4 backspace?
225's should fit. I have 245/60/15's on the back of my Valiant which also has stock wheel wells. They're mounted on Wheel Vintiques steelies that are 15" x 8' with a 4 7/8" backspace. They did rub at first, but my leaf springs were shot. I put new ones in that were arched 2" over stock - problem solved. I have a 7 1/4" rear with 9" drums. I don't think the width of the rear makes a difference, the spring perches are in the same place as the larger rear would be.
Not sure if that helps, perhaps it gives you an idea of what can be done.
225's should fit. I have 245/60/15's on the back of my Valiant which also has stock wheel wells. They're mounted on Wheel Vintiques steelies that are 15" x 8' with a 4 7/8" backspace. They did rub at first, but my leaf springs were shot. I put new ones in that were arched 2" over stock - problem solved. I have a 7 1/4" rear with 9" drums. I don't think the width of the rear makes a difference, the spring perches are in the same place as the larger rear would be.
Not sure if that helps, perhaps it gives you an idea of what can be done.