Father-Son 1974 Duster Project

You mentioned 3.5" back space. If everything back there is Stock you may want to remeasure. It'll likely turn out more like 4.5" back space on a 15x8 if you want 275 60 15 tires. Love the car!

Cley
The wheels I have now are 4.25 backspace and if I put a 275 on those wheels, the tire hits the leaf spring. So my thinking is if the back space is reduced by 1 inch the wheels will move further away from the center of the car and push the tire out from the center and give me clearance on the leaf spring. Does that make sense?