This is a '71 with 17 x 9.5" (5.5" BS) and 17 x 11" (6.25" BS) Cragars.
The tires are 275/40/17 and 315/35/17, and the car is sitting on a stock suspension setup.
A 315/35/17 tire has dimensions of 12.5" x 25.7" and a 275/40/17 has dimensions of 9.5" x 25.7".
That means the fronts and rears on this car are matched for the same tire height.
These look a little short to me personally, not enough meat. If you went to a taller aspect ratio, say maybe a 315/45 out back, overall diameter would be 28.2" tire for the rear, and a 315/40 would give you a 26.9" height, and both of those will add a little meat to the sidewall.
This is a good ballpark area to start from, huh?