Tim love your Duster. You have had the Mopars but didn't you work for Ford? You are correct on the Magnums on the small bolt pattern on the Duster, Darts and Demons. Though in 76 when the Aspen and Volare came out you could get the Magnums on them. Btw the Aspen and Volares were awful rust bucket but working at a Chrysler store in the 70's I can tell you they were really nice driving cars for small cars.