According to Ford, the KR designation on the Mustang Shelby GT500 stood for “King of the Road.” However, legend has it that Shelby heard through the grapevine that Chevy was planning on using the moniker on a competing model, so Carroll simply beat them to the punch. Whichever is true, the 1968 GT500 KR was the fastest Shelby car produced to date. Though factory rated at 335 horsepower, it was believed the true horsepower rating was between 435-500.