Is the rear window trim the same for all 3 years or is it different? Also does it differ from a 2 dr. hardtop to a sedan?

I assume you mean the outer stainless window mouldings.67 is all by itself.68-76 2 door hardtop mouldings are all the same-4 doors are totally different.One exception is that the 75-76 models used aluminum mouldings[sometimes].
So you could get the mouldings off any 68-74 2 door hartop Dart or 71-74 Scamp.