Demon door?? Which others fit?

Alright, you got me, I was wrong. I'm not sure I'd call it major surgery, but it does require a lot more work than I thought.

The door skins and shells ARE the same. But, as I already said, the window mechanisms, tracks, etc, are all different.

What I didn't know is that there are a couple of internal brackets that are also different. On the Duster door, there are two internal brackets at the top of the door that are used to mount the window guides that are not present on the Dart doors. On the Dart doors, there is an internal bracket for the vent window that is not present on the Duster doors. All of these brackets are just spot welded to the door frame on the inside of the door, but unless you wanted to spend a lot of time custom fitting a set of brackets, you would need donor brackets from the model you wanted.

Finally, there was another thing I didn't even realize- the mirror location is different between a Dart and a Duster/Demon. On the Dart's, the mirror is located at the post for the vent window. That location is about 4" further back than on the Duster/Demon doors, which don't have a vent window to worry about.

So, while the skins and shells are the same, swapping the window mechanisms between models is a big enough problem that it's probably not worthwhile for most folks. The only way it would really be feasible is if your original doors were badly damaged or rusted, and you had a clean set of doors from the wrong model car. Then you'd have the internal brackets to swap over. That would be on a similar skill level as say replacing a tail panel or doing a quarter panel section though. Not really hard, but definitely an operation that requires some skill to get right.