Back in late 1967, Carroll Shelby learned that Chevrolet was planning to introduce a special performance version of the Corvette they called “The King of the Road.” He liked the name, so when he found out the name was unregistered, he put the copyright on it. Shelby wanted to present a special version of the GT500 to spite Chevrolet. Since Ford had just introduced the 428 Cobra Jet, its legendary muscle engine, this was the perfect time to install it into a Shelby. Also, they wanted to add some performance goodies and go-fast options to create one of the most sought-after muscle cars of all time, the Shelby GT500KR or King of the Road (via Car and Driver).
Although they rated the 428 Cobra Jet at 335 HP, everybody knew the engine delivered more than 400 HP and 400 lb.-ft of torque. Ford limited the production and loaded the GT500KR with interior trimmings and luxuries. Unfortunately, they only produced the GT500KR for the 1968 model year, dropping the version for 1969. Also, in 1968, Shelby stopped making Mustangs for Ford. So, they moved the Shelby Mustang assembly from California to Michigan. Even though Ford continued to offer Shelby Mustangs until 1970, Carroll was not a part of the engineering team after 1968.