1963 Dart L6 Heater Core

Video of the box removal (closest to our year I know of and I think it's the same box up through to the early 70's anyway)



Video of the rebuild process.



Link to the box rebuild kit I would recommend since you're already gonna have it all out anyway.
Mopar A Body 63-66 BASIC NON AC Heater Box Rebuild Restoration Seal Gasket Kit