One other thing I will add...the front end of a 1967 Chevy pickup was completely different from the front end of a 1953 Chevy pickup. It was built with independent suspension, fully adjustable caster, camber, inclination angle, sway bar, etc and your 1953 truck only has adjustable caster angle. Everything else in your front end is fixed. And unlike the 1967 truck, when one wheel goes up, things change on the other side since you have a straight axle.
If you study all the available tire sizes for a 15 inch wheel with a 6 inch rim, I think you're going to discover a 27" diameter and a 205/75 R15 tire is your best choice. Good luck!
