For the 1970 model year, Lincoln made good on its 1958 plan to commit to a nine-year design cycle, giving the Continental its first complete redesign for the first time since 1961. During the 1960s, while sales of the Continental had remained relatively steady throughout its production, the engineering of luxury cars had begun to change among its competitors; to increase design commonality (and lower production costs), Cadillac and Imperial shifted away from brand-specific platforms (with the latter adapting to shared bodyshells with Chrysler). For the redesign of the Lincoln model line, the Continental grew in size. While sharing no visible body panels, Lincoln adapted the chassis of the Ford LTD/Mercury Marquis (shifting to body-on-frame construction for the first time since 1957). In another effort to maintain design consistency, the 1970 Continental was produced through 1979 with only gradual updates. Along with the mandated addition of 5-mph bumpers, in 1975, the roofline was redesigned (to visually differentiate the Continental from the Mercury Marquis).