In 1971, Dodge gained a version of Plymouth's popular Valiant-based fastback Duster and was to be named the Beaver, but the vehicle was renamed the Dart Demon.
As was the case with previous Dodge rebadges of Plymouth Valiants, such as the 1961–1962 Lancer, sales of the Demon lagged behind those of the Duster. With optional hood scoops and blackout hood treatment, the car was advertised a high-performance car. The Demon's Dart-type front fender wheel lips and Duster-type rear wheel fender lips reveal the car was essentially a Duster with Dart front sheetmetal and other minor styling changes. A new audio option became available for 1971: Chrysler's Cassette-Recorder. Unlike the 8-Track tapes, the cassette player was relatively compact, and it was mounted on the console or on its own floor-mount casing. This unit offered an available microphone in which one could record their own dictation.
The Swinger 340, Dart's performance model, was replaced by the Demon 340 with optional hood scoops and blackout hood treatment. Chrysler Canada, though, did build a small number of 1971 Swinger 340 hardtops based on the Swinger Special for two dealers in Western Canada. In 1971, Chrysler abandoned their longstanding corporate practice of installing left-hand threaded wheel studs on the left side of the vehicle; all wheel studs on the Dart thenceforth used conventional right-hand threads.
The Dart Demon nameplate was replaced from 1973 with Dart Sport.
Source: Wikipedia, 2011