I have a 1975 dart sport with those extensions. I'm pretty sure they would fit a 1973. I your still looking I will sell them at a very reasonable price.
This is great. Finally a site dedicated to A-body Mopars.Just the incentive I need to get back to work on the Dart Sport,it's a "74" I've had this car since I was eighteen and am now fortyeight.Anyway ,thanks great site!