The Duster was introduced in 1970 to compete with Ford’s slightly smaller semi-fastback Maverick compact and Chevrolet’s slightly larger semi-fastback Nova. Unlike the Maverick and the Nova, however, the Duster only was available in a two door coupe.
1974 was a banner year for the Duster. Buyers continued to come into the Plymouth dealers in high volume, driving away every Duster that could be built. Style wise, the 1974 was a pass. No major changes at all, except under the hood. The 360 cubic inch V-8 was introduced to replace the 340.
You can read more Duster history here>>