Heater core isn’t fitting in Plymouth Duster

MOPAR4Me said
In post #1 you say your car is, "1976 Plymouth Duster without AC"

In post #4 you appear to say you got the one without AC, and went back and got the one for an AC car.

If you do have a car without an AC, then the one in the pic is wrong for your application.

These should be your part numbers if for an AC unit, Chrysler: 3502462, 3502765, 3780551

It doesn’t have AC at the moment, but it has all the hook ups for AC. The one without AC looked nothing like the original, but the one with AC looks the same as the original.