Pontiac Grand Prix X-400 Show Car, 1963. Built by GM Styling using a stock Catalina Convertible powered by a supercharged 421ci Pontiac V8 engine built by racer Mickey Thompson. Though it previewed the concept of a Grand Prix convertible none was offered for sale until the second generation in 1967 and then only for a year. X-400 show cars were built each year for 1959, 1960, 1962, 1963 and 1964. The car still exits in the hands of a collector