68 barracuda tire size

Getting ready to install 255/65/15 on 15x8 on the rear of the 69 FB barracuda 5.5" BS on a 1" adapter (4 to 4.5 lug) anticipating 1.5"+/- clearance between the tire and leaf and 1"+/- at fender. height is not an issue, I have air shocks at 25psi and that leaves plenty of wheel well. I might drop the shock pressure down a few pound s after install.