1966 Dart Factory AC Fittings

It's not pipe thread, no. Those are "Tube-O" fittings into and out of the evaporator—the factory setup first available in '65 did not use flare fittings, or at least not many of them, versus the knee-knocker add-on units (including Chrysler's own Cool Comfort and Airtemp-branded units) which used only flare fittings.

Take a look at the bottom line of this chart and you should find the info you need.