Destined to disappear, the muscle cars remained in production for another year, for 1971. 1971 was also the last year for the Plymouth GTX, which from 1972 became only a variant of the Road Runner. The 1971 vintage ushered in a shorter wheelbase and a two-door body only. Fortunately for fans, the sportier engines remained in production for a few more months, before being outlawed by anti-pollution laws.