Heater Core

I got my '64 Dart heater core from Performance Radiator https://www.performanceradiator.com/locations.php Great fit, bolted right in.

And I second Detroit Muscle for the hearer box rebuild kit. The kit covers many model years, so I gave away the unused portion on the forum. TAKE LOTS OF PICS FROM LOTS OF ANGLES WHEN TAKING APART!! You can't take too many pictures. Really!

Good Luck!