Upper and Lower Ball Joints

Yes I have a 71 Duster. The setup I am using came from a 72 Dart. Now when I buy lower ball joints would I buy them for the car? (71 Duster) or the setup? (72 Dart) I found some MOOG on Jegs for $47 say they fit 73-76 Duster, says nothing about 70-72 but that it fits 62-76 Dart. Would I be okay using these because the whole setup is from a Dart? I hope I did not confuse you ..