The '71 Duster 340 was supposed to exclusively have the shark tooth grill and the matching shark tooth tail light panel that went on the '71 Demon. You would know it was the 340 coming or going. All other Dusters would have the standard grill and tail light panel. However, since Dodge cried foul on not having their own version of the Duster, Plymouth had to give them the body with the shark tooth tail light panel. So, if you have a '71 Duster 340, replace the tail light panel with a Demon repop and TAH DAH, you will have the Duster 340 that Plymouth wanted you to have back in '71.
