Patching on an old, rotten radiator core can be a never ending nightmare. Even a replacement core from 40 or 50 years ago is still- - - - -OLD!

Either bite the bullet and buy a new copper core radiator- - - -"Buy once- - -cry once"- - - - -or be willing to replace a 3rd. world repop radiator two or three times for around the same cost. Whatever you do, be sure to also upgrade the heater core to the same pressure rating as the radiator so you can take advantage of running pressurized coolant that has a higher boiling point that the "zero pressure" system you have now.
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
Love your enemies and drive 'em nuts!