1965 273 valve seals - different than later model?

Every manufacturer will probably have a different part number. They will be umbrella seals and the 65's are the same as the 67 's. Mopar kept the same valve stem size on the small block heads until the Magnum heads came out.
I'd even bet they were the same seals as the poly engines. 3/8 stem, that's what they got.