Duster 1970-1972 and 1973+ Door Difference?

Can someone please help me figure out what the differences between the doors are on the 70-72 Dusters and my 73. I need to get the window felts and the door weatherstrip, but everywhere I find only shows them for 1970-72. Why won't they work? If they won't, where can I get the right ones?
Thanks,
Jon