Pressure Rating For Car Rims?

[saltfever]

I found a nice set of car rims I want to use for my trailer. Trailer tires are generally higher pressure (50-65 psi) compared to car rims (usually 25-35 psi). I have looked the rims over for any DOT numbers or pressure ratings but can't find anything. Does anyone know how I can find the pressure rating (or load rating) of a standard set of passanger car tires from the 60's?

[38Chevy454]

Not necessarily a specific answer, but my std dual axle car trailer has 60's Buick chrome wheels, such as from an Electra or other big car.  I run 15 inch trailer tires at 50 psi and have not had any troubles with the wheels.  I guess I never thought that the increase from 32/35 psi up to 50 would be any cause for concern on a steel wheel.  YMMV..........