The Ford Shelby Mustang GT500 Super Snake was a special variant of the S-197 I Shelby Mustang that was offered beginning in the 2007 model year. The S-197 I GT500 Super Snake was based on the standard S-197 I GT500, but with substantial performance and appearance upgrades that were performed by Shelby in their Las Vegas factory. Notably, engine performance was massively increased with a variety of superchargers available, power ranged from 604hp to over 725hp depending on which supercharger was used. The Super Snake package was offered on both convertible and coupe body styles, with a 6 speed manual sending drive to the rear wheels. A limited production offshoot of the Super Snake, known as the 'Shelby 427', featured special badging and trim intended to commemorate the 2009 Shelby 427 NASCAR race at Las Vegas Motor Speedway. Production of the S-197 I Ford Shelby Mustang GT500 Super Snake ended in 2009, but the variant would continue life as the next generation S-197 II Ford Shelby Mustang GT500 Super Snake.