Built alongside the Bristol 412, the 603 was released for the 1977 model year. The car was built in four series: the 603, 603 S2, 603 S3 (Britannia and Brigand), and the 603 S4 (Blenheim). Each series was updated with minor modern styling cues. It remained a 2-door coupe and still powered by Chrysler V8s and even a turbocharged version much like the 412. The Blenheim would be the first to offer a four-speed automatic with overdrive. The 412 would stay in production until the company's closing in 2011.