The biggest problem with the older radiators is that they can't be pressurized due to their type of construction. I'd suggest upgrading to a more modern style, or at least have your original radiator rebuilt to use a tubular core. Every pound of pressure raises the boiling point 3 degrees F. Older "honeycomb" style radiators can't handle over about 3-4 pounds of pressure, and the filler neck usually won't accept a pressure cap. Ditto for the heater core- - - -unless it's reworked, about 4 PSI will be max.
Jerry
