The Shelby Mustang is a higher performance variant of the Ford Mustang which was built by Shelby from 1965 to 1968, and from 1969 to 1970 by Ford. Following the introduction of the fifth generation Ford Mustang, the Shelby nameplate was revived in 2007 for new high performance versions of the Mustang but this time designed and built by Ford at its assembly plants.
For 1968, the Cobra name was applied to both models, and they were now marketed as the Shelby Cobra GT 350 and the Shelby Cobra GT 500. The solid lifter K-code engine was discontinued by Ford so Shelby used the hydraulic lifter 230 hp 302. It produced 250 HP with the high rise intake but was not equipped with Shelby headers in order to make room for power steering. The early 1968 GT500 used the Shelby installed 428 Police Interceptor with a single four barrel carburetor rated at 360 HP.
Beginning in April 1968, Ford began factory installing a version of the 428 engine known as the "Cobra Jet". The GT 500 was subsequently know as The GT 500-KR. The initials KR stood for "King of the road." Ford rated the Cobra jet at 335 horsepower (250 kW), but with 440 foot-pounds of torque at 3400 RPM, the horsepower was considered significantly underrated. Shelby's KR engine was left stock adding die-cast aluminum valve covers with "Cobra Lemans" to note Ford's FE engine family victory over Ferrari at Le Mans in 1966 and 1967.