I have been down your road more than once. Although you don't want to, I would highly recommend hanging the original radiator on the shop wall and installing a quality replacement. Your chasing problems with metal that is over 40 yrs old, has gone through untold heat cycles with who knows what corrosive and electrolytic contributors that affected the metal "back in the day".
If you invest enough time and money you might, someday, have a non leaking radiator...but will you ever really trust it? I wouldn't.
Just my two cents.