Any of the Duster/Demon/Dart Sport doors from '70-'76 will "work", meaning they'll all bolt into place, open, close, seal at the window etc. Having a '74 door with your '73 is nice because it will use the same interior panels as a '73, so they'll at least match each other when fully assembled. Internally though they're totally different- different glass, different regulators, different window hardware. Not a big deal if both doors are complete, but if they're not it means sourcing two different sets of glass and hardware. Most stuff is sold in pairs so it may be a bit of a headache.
So what I wanna know is why you didn't provide any useful information? Clearly you know everything there is to know, so the nice thing to do here would have been to answer one of the OP's questions. Or post something useful.
