The Chrysler 300 "letter series" were high-performance luxury cars built in very limited numbers by the Chrysler Corporation in the U.S. from 1955–1965. Each year's model used a new letter of the alphabet as a suffix (skipping "i"), reaching 300L by 1965, after which the model was dropped.
The 300 "letter series" cars were among the vehicles that focused on performance built by domestic U.S. manufacturers after World War II, and thus can be considered one of the muscle car's ancestors, though much more expensive and exclusive.
Chrysler has recently started using these designations again for sporting high performance-luxury sedans, using 300M from 1999, and continuing the 300 series with a new V8-powered 300C, the top model of a relaunched Chrysler 300 line, a new rear-wheel drive car launched in 2004 for the 2005 model year. Unlike the first series, the second does not have 300 hp (220 kW) engines, except for Chrysler's current top-line 300C models.
The 1965 300L was the final year of the traditional letter series. A complete restyle, with crisp lines, slab sides and a tall "greenhouse"—styling cues introduced by Elwood Engel when he succeeded Virgil Exner as Chrysler's styling boss—brought a sleek mid-1960s linear look to the cars, and dropped the panoramic windshield that had disappeared from other Chrysler models in 1961. The cross-ram engine was no longer available; the 413 cu in (6.8 L) engine with regular carburetion and inlet manifold was the only one supplied. Practically every feature on the 300L could be ordered as an option on the regular 300; the only absolute difference was the '300L' badges. 2,405 coupes and 440 convertibles were sold.
Source: Wikipedia, 2013