The Dart Sport has a header panel in front of it. The Duster goes all the way to the front and overhangs the grille. Gotta change the whole front clips if you want to keep it looking decent.
Notice how the Dart has a single peak in the middle, and the Duster has more of a bulge? Also, the Duster hood carries over the grill, whereas the Dart hood stops and has an extra panel ahead of it. The 73 - 76 Dart hood is the same as a 69 Barracuda hood..