Tire size substitution charts are on websites for Vintage Car Connection and Tire Rack. Vintage Car lists tire sizes up to 1972 and displays equivalent newer tire sizes. The Tire Rack chart covers sizes prior to 1980 and identifies the closest modern tires.
Substitution charts are often used for restoring classic cars. The recommended substitute tire is not necessarily an exact match for the original tire. Older cars tend to have narrow wheels, so they need narrow tires. Without the proper tire diameter, the accuracy of the speedometer is affected. In addition, a poorly chosen replacement tire potentially impacts the visual appeal of the car.