255/50/15 on a 8 inch rim 71 valiant?

That would be a really tight fit. I have 235/60R14's on 6" rims with SS springs and I don't have much clearance. I used to run 225/75R14's on the same rims when the springs were stock and literally had my hand stuck between the tire and wheel well. I needed help turning the tire backwards to get my hand out.