The new radiator will allow you to run a pressure cap that raises the boiling point 3 degrees for every pound of pressure. Then the condition of heater core becomes the limiting factor. Original cores will only handle around 4-7 PSI, less if they're in poor condition. Upgrade the heater as well as the radiator and you'll be able to run the pressure up to 12-15 PSI or so and not worry about boil over below 240 degrees or so.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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