Tire size with Columbia rear end

[blucar]

The 15" wheels/tires would be a nice addition to your car. Radial tires would also be a plus.

I would suggest that you use '57-66 Ford F100 wheels, they will be in the five inch wide range. They are a direct fit to your car and your stock hub caps will fit perfectly, you will have to purchase 15" beauty rings.
Be careful buying the 15" wheels, the early 15" wheels are narrow, in the 4.5 range and will not have the DOT spec's stamped into the rim. The later model '57-64 F100's will generally have the spec numbers stamped into he rim.
The '67-91 F100-150 wheels will also work except they have external hub cap knobs like the '49 and later Fords/Merc.s.