Debute of this car was at the Le Mans 1964 race for Ford motor company with Ritchie Ginther-Masten Gregory at the wheel. It was a DNF as result (gearbox). The car ran also in Reims, again a non finish due to gearbox issues. After that, the car was sent to Nassau (DNF). After Nassau GT/103 and GT/104 were hastily packed off to Shelby American, Inc. in Los Angeles and put through exhaustive testing at Riverside and Willow Springs by Ken Miles. Several problems became apparent, most notably in the areas of engine cooling, gearbox, brakes, high speed roadholding and overall weight. Aerodynamics also remained problematic. Although much had been learned in wind tunnel testing, the GT40 did not behave on the track as testing data projected it would, for several reasons. At the time only limited background data existed for testing automobiles in the wind tunnel; reproducing ground effect was almost a complete unknown because it is irrelevant to aircraft design, and scaling a car for wind tunnel testing demanded much higher precision than was initially thought.
Along with the experience gained over the previous season, the new testing resulted in several changes to the prototypes. Removing the dry sump oiling system and its associated plumbing saved 75 pounds and allowed the nose and internal ducting to be reshaped, improving cooling and increasing downforce for reduced front lift. New internals for the Colotti were manufactured by Ford to handle the higher torque and horsepower of the Cobra-spec 289 CI engine, which offered another distinct advantage. Because of their vast experience with the 289, Shelby mechanics could tailor GT40 powerplants to any circuit and race distance. While suspension geometry remained mostly intact, the basic components were strengthened for increased durability. The Borrani wire wheels, which had barely provided adequate cooling to the brakes, were replaced with lighter and stronger magnesium wheels.
During the 1965 season, 103 won the 2000 km of Daytona with Ken Miles and Lloyd Ruby for Shelby America Inc. This was followed by a podium finish (P02) in the 12 hours of Sebring (#11) and in the 1000 km Monza (P03) with Miles and Bruce McLaren. Last race in 1965 at the Nurburgring ended with a driveshaft failure in lap 6 (#12).
In the autumn of 1965, the American pilot Bill Wonder contacted Shelby in order to buy a Cobra. Instead, the gentleman-driver was offered a GT40, the Daytona winning car.
Fitted again with the 289 high performance engine and mated to a ZF five-speed gearbox, GT/103 was sold in January 1966 by the FAV factory works department to Bill Wonder. He requested that it be painted deep red, but specified that the original, race-winning, Daytona blue interior be left untouched. Wonder purchased GT/103 because it was still a competitive, proven, reliable racer and he treated it as such. He privately entered GT/103 in several races per year including Daytona and Sebring every year from 1966 until 1970 when he decided to retire the car from competition. At that point, GT/103 had raced regularly for six full years and was stil in excellent working order after Daytona 1970 after a P08 finish. In order to remain competitive, Bill Wonder had updated GT/103 with the latest factory parts when they became available to him. Modifications included the fitment of Ford MKII brakes, modified single outlet front insert, Koni shocks and even wider eight inch front and eleven inch rear Halibrand wheels.
The car, in 2001 still owned by Bill Wonder, was regularly spotted in historic race events.
In the Monterey auction 2005 chassis 103 was sold for $2,502,500. The car was to be seen at the Larry H.Miller Museum, located at Miller Motorsports Park in Tooele, Utah. There the car was restored. After a decision to slowly start returning the car to its 1965 race winning glory, the deep red paint was removed and the period, correct 1960s bodywork smoothed to accept a fresh coat of blue paint, white stripes and the number 73.
