Aftermarket vendors like Classic Industries has 69 Dart listed separate from 67 and 8 Dart. B'cuda listed separate from those. Not a definite answer but a clue that there must be some difference.
The factory list different numbers for the Dart and Barracuda, probably because the body is a different shape.
The top and all associated hardware is probably the same, the boot and the trim are probably the only differences.
The interior side panels are different although interchangeable.