The Plymouth Road Runner is a mid-size car with a focus on performance built by Plymouth in the United States between 1968 and 1980. By 1968, some of the original muscle cars were moving away from their roots as relatively cheap, fast cars as they gained features and increased in price. Plymouth developed the Road Runner to market a lower priced, basic trim model to its upscale GTX.
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. The interiors could be ordered with 6-way power leather seats, thick deep-pile carpeting, and additional sound-proofing was installed. A/C, and power steering could be had, except on the Hemi. 1971 was a high-water year for ride and handling for the Road Runner. The overall length was increased, but the wheelbase was shortened an inch. It also saw the introduction of the 340-4bbl option, and a detuned 383 "Road Runner" engine with 8.7:1 compression, hardened exhaust valve seats, and power dropping to 300 hp (224 kW). In return, Road Runners with the 340 and 383 engine received a standard insurance rating without the costly premiums normally tacked onto muscle cars. The 383 would now run on regular gas.The 440+6 and 426 Hemi were available, though this would be the last year for them. The tall axle ratios with the 8 3/4" Chrysler and Dana 60 rear ends, as well as the wide and close ratio 4-speed transmissions could be had with any of the engine choices, though few cars were built with the six-pack or Hemi engines. Aerodynamics were much improved over the first generation Road Runners, resulting in much-improved high-speed handling.
Source: Wikipedia (original)