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 , but with of torque at 3,400 rpm, the horsepower was considered significantly underreported, as it was later found that the car made . 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.