Possible dumb question

What are you replacing? '73 & '74 share many of the same parts (Taillights, Grille, etc)

The Interior can be 1973 - 1976 (Duster/Dart Sport), except the Kick Panels, A-Pillar Trim and the Steel Moulding above the doors, those will fit from 1970 - 1976 (Duster/Dart Sport/Demon)

The Side Marker Lights can come from any A-body 1972 - 1976 (the same lights were also used into the 80's on some other cars).

Plus so much other stuff, and depending on how much swapping around you want to do, any part (1970 - 1976) Will fit provided you swap the necessary stuff.