One place I have stumbled across for classic radiators and heater cores.

www.caparadiator.com

They have a section for classic radiators and classic heater cores. They prefer the older stuff so this is right up their alley. They are currently doing a radiator for me for a 51. They will keep all the correct build and date codes. Neat little shop. Have a look.

Royv

1951 Chevy 1/2-Ton 5-window