1980 saw the introduction of the Seventh Generation of Ford F-Series. The 7th Gen F-Series was redesigned with an all-new chassis and larger body; this was the first ground-up redesign since 1965. The exterior styling of the truck was redone to improve aerodynamics and fuel economy. Four main variants were built, the F-100, F-150, F-250, and F-350. Also offered were the Medium Duty Ford F-Series (F-600, F-700, F-800). In a move toward fuel efficiency, Ford dropped the M-Series engines (the 5.8L 351M and 6.6L V8s) in 1981, replacing them with the 4.2 Liter and 5.8 Liter V8 engines from the Panther platform, which were offered alongside other inline six, V6, and V8 options. 1983 marked the final year of the F-100, making the F-150 the lightest pickup available on the market. Ford produced the seventh generation until 1986, when they introduced the Eighth Generation F-Series.