Chrysler built its 'Muscle Cars' on the B-body, with the Dodge Charger and Plymouth Road Runner, but the Plymouth Duster was the same recipe applied to the 108-inch A-body Valiant. From the windscreen forward the Duster was Valiant, but behind it was a semi-fastback coupe with tumblehome sides. Neil Walling designed the Duster constrained by having to retain so much of the Valiant on which it was based. The Duster was launched for 1970 with a choice of two slant-six engines and three V8s. A Duster 340 was also launched as a performance orientated version with its 5,563cc (340) 240 bhp Hemi V8. Evolution of the Duster was slow, with nothing much more than grille and rear lamp revamps until its demise in 1976. Engines became emasculated due to emissions regulations, and the 340 was upgraded to 360.