I've only owned a Plymouth Valiant and now a Dodge Dart. Not sure about the Duster but it sure looks the same. Here are a few pics of when this bumper was mounted to my Valiant.
Up for sale is this front bumper that came off my 1972 Plymouth Valiant. Its in great shape, no nicks or dings. Was re-chromed by Superior Chrome a few years back. Asking $150 + shipping. I'm located in Orlando Florida. Thanks