Dr.Jeff
True Classic
In the old days of "real" radiator repair shops you could watch as they "rodded out" the core of your old unit. Amazing what would come out of a semi-functioning core. And more amazing how much difference it makes.you have an aging, starting to plug, reduced-flow radiator
Also keep in mind there are other aspects of the cooling system that can cause the same symptoms if they are not functioning correctly. Basically everything must be in proper condition for the system to work as it should.