Has anyone found a source for these?
Yes........both......the OEM way is still done but you will pay more for it for sure and it really depends on how bad the original is. The AACA and VCCA magazines frequently run vendor ads for folks who handle the older OEM style rebuilds as well.
I just listed a right and left heater core assembly from a 56 Sedan de Ville on Ebay. My seller name is cadparts58
Hi RickI am just starting a restore/repair adventure in a 56 coupe. If I need heater cores any chance you might be interested in selling a set ?Thanks Dan