In regards to comments being removed, my comment was also removed. I stated that not all 340 dart swingers came with roof rail drip moldings. I believe that it will be on the fender tag (M21). I have an original paint car without said moldings. It was an option on a 340 swinger. Still have the car and had at least one other the same. I also stated I didn't want to this to turn into an argument but was trying to help both parties out. If the numbers on the body, vin tag, and fender tag match its a good chance it's legit. No guarantee that these numbers weren't transferred or transplanted. Attached pics of my original paint car. Hopefully you can see the roof rail.
Good luck to all