You should be able to use any fender Ie I ran 68 dart fender on my 74 swinger you just have to move the marker light but the wheel well is a different shape on a plymouth vs a dodge. A dodge flares out and a plymouth doesn't with the acception of a scamp and demon the rears on these cars for a scamp flairs and a demon doesn't but that was because they didn't modify the rear quarters after turning a swinger into a scamp or a duster into a demon/sport. Don't know dusters that well but if a 73 has the 74 front end then the dart bumper will stick out too far from the body.
Dan