Tire size question

I wonder if that 10.0 is correct
325/50-15s are a tic over 13 inch section width, and the fit into my stock 68Barracuda tubs. Now the tread is only about 10. so the 3 inch difference has to be made up for; half to the inside and half to the outside. so that would make it 10 + 1.5 = 11.5 from the outside edge of the tread to the zero point of the inner fender. My sidewalls are flush to the outer body line. And the tire is about 1 inch below the bottom edge of the fender lip. I bent that lip up and out of the way.The rear suspension is stiff enough to not let the lip kiss the sidewall. So I am estimating 10 + 1.5 +.75 + 12.25 from the bent-up lip to the inner fender, and 13 from the painted surface of the body to the inner fender. With 1.5 mini-tubs, you should have 14.5 from paint to inner, and about 1.25 less if your lip is virgin. So That would be 13.25. If your springs are moved inboard, to the same plane, then you should have plenty of room for 325s, without bending that lip. The backspace will have to be very carefully worked out tho.....