The Shelby Mustang is a high-performance variant of the Ford Mustang which was built by Shelby American from 1965 to 1968, and from 1969 to 1970 by Ford.

Following the introduction of the fifth generation Ford Mustang in 2005, the Shelby nameplate was revived as a new high-performance model, this time designed and built by Ford Beginning in April 1968, Ford began factory installing a version of the 428 engine known as the "Cobra Jet".

The GT500 was subsequently known as The Cobra GT500 KR. The initials KR stood for "King of the Road." Ford rated the Cobra jet at 335 hp (250 kW), but with 440 lb⋅ft (597 N⋅m) of torque at 3,400 rpm, the horsepower was considered significantly underreported, as it was later found that the car made 435 hp (324 kW).[citation needed] 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.