Where to buy 1964 New Yorker heater core, factory a/c car

[superbee_68]

I'm working on a buddies 1964 New Yorker. We rebuilt the motor and are about to put it back in. He wants to go ahead and upgrade the a/c compressor and change the heater core. I can get a compressor upgrade kit from classic auto air I believe. Anyone have any experience with these? Where can I get a heater core? I see them available for non-air cars. Any help is much appreciated.