41 3/8" Narrowed 8 3/4 for 65 barracuda

Most of the time it's how ever the owner decides to do it because there are several different ways to do it. I don't have an older A-body or I could take measurements of the rear frame rails and know more. Measure your frame rails and see how far they are apart. If they 31.5 center to center then that means the guy relocated his springs to the middle of the rails instead of the outside of them. He could have also relocated the springs to inside of the frame rails. You'll just have to measure yours to see where the springs would be when their 31.5" center to center.