Ruby also had two endurance racing victories in the 24 Hours of Daytona (1965–1966), both times partnering with Ken Miles. Ruby and Miles teamed up to win the 1966 12 Hours of Sebring and the 1966 World Sportscar Championship. Ruby was scheduled to drive in the 1966 24 Hours of Le Mans, however he was forced to withdraw due to spinal injuries suffered in a plane crash. A year later, he teamed with Denny Hulme in a Ford GT 40 Mk IV for the 1967 24 Hours of Le Mans. Ruby played a key role in Ford Motor Company's GT40 program in the mid-1960s. He also raced in the 1961 United States Grand Prix.