Mk II GT40 achieved great success, with Shelby American's wins at Daytona, Sebring and Le Mans earning Ford the International Manufacturer's Championship in 1966. Shelby American cars finished first (Miles & Ruby again) and second (Gurney & Jerry Grant) at Daytona, first at Sebring (Miles & Ruby), and first (McLaren & Chris Amon) and second (Miles & Denny Hulme) at Le Mans. Gurney and Grant would have finished second at Sebring except their car broke down on the last lap and Gurney pushed it across the finish line, automatically disqualifying them. During the 1966 season Shelby and Ford were already developing a more advanced version of the GT40, known early in its development as the "J-car". On August 17, 1966, only a couple months after the race at Le Mans, Ken Miles died at the wheel of a J-car while conducting high-speed testing at Riverside. The J-car was re-engineered with improved safety features and better aerodynamics, becoming the GT40 Mk IV. In 1967 the Mk IV won the only two races they entered, at Sebring and Le Mans. McLaren and Mario Andretti won the race at Sebring, while Gurney and A. J. Foyt won Le Mans, with McLaren and Mark Donohue in fourth. After the 1967 season the FIA changed the rules governing prototypes, and the 7.0 L engine used in the Mk II and Mk IV GT40s became redundant. Ford wound up the Ford Advanced Vehicles group and Shelby American withdrew from the World Sportscar Championship, transferring control back to John Wyer's J.W. Automotive Engineering (JWA). JWA GT40s won the 1968 and 1969 races at Le Mans, giving the GT40 program an unprecedented four consecutive wins (matched only by the Porsche 956 in the 1980s). Ford Mustang While Shelby American was building and racing Cobras and Daytonas, Ford introduced the new Mustang at the New York World's Fair in April, 1964. Ford vice-president Lee Iacocca promised that the car would be "a sports car suitable for street use or competition" in his introductory speech to the press. In reality the car's sporting credentials were somewhat lacking, and Iacocca hired Shelby American to develop a version of the car suitable for racing. The Shelby Mustang GT350 was created, with upgraded intake and exhaust manifolds, carburetor, rear axle and brakes installed at Shelby American's shop in California in place of the standard Ford parts. With work on the GT40 program and