Dumb question - difference between Dodge and Plymouth

The only duster that is at the top of the food chain as far as value goes is called a Dodge Demon, Funny how they put a dart nose and different tail lights in it and made a more valuable and better looking car. A friend of mine was looking for a 340 or 383 Dart GTS or Swinger for a year now ran across a half dozen 340 Dusters in excellent shape he could of picked up between $15,000 and $20,000 but every Dart he found where in the $25,000+ range. He finally bought a 67 318 Dart GT for $18,000 and it was only 85% to 90% finished.