Plymouth Road Runner 1971 - 1974

In 1971, the coupe bodywork was completely changed to a more rounded "fuselage" design in keeping with then-current Chrysler styling trends, including a steeply raked windshield, hidden cowl, and deeply inset grille and headlights. In a departure from previous thinking, the B-Body two-door bodies shared little if any sheet metal, glass, or trim with the four-door bodies. The convertible was canceled. 1971 was a high-water year for ride and handling for the Road Runner. The overall length was decreased, but the wheelbase was increased, and a rear sway bar was used in place of staggered rear leaf springs, resulting in better handling and cornering without the stiff ride. Aerodynamics were much improved over the first generation Road Runners, resulting in much-improved high-speed handling. 1972 saw new emission regulations drive power down and 1/4 mile times up. The 1972 model was nearly identical to the 1971 with a few minor changes. The grille design was cleaned up, and the tail lights were changed to match the new aerodynamic look of the grille. The optional bumper guards for 1972 included a rubber strip surrounding the tail lights and a rubber strip below the grille. The big difference came in the engines, with the big-block 383 being replaced by a larger-bore 400 CID version and a small-block, the 340, now optional for the first time. Also, for the first time, a 440 CID engine with a 4-barrel carburetor was available. This engine was the basis for the "GTX" package (as the GTX was no longer available as a separate model) that was available on Road Runners from 1972 to 1974.

Source: http://en.wikipedia.org/wiki/Plymouth_Roadrunner