After developing the GT40 for two years, Ford finalized the car and put it into regular production. A total of eighty four production versions were completed at Ford’s Advanced Vehicle facility in Slough, England. This production number was sufficient to homologate the GT40 and after GT40P1084, Ford Advanced Vehicles was dissolved.

Following the departure of Ford Advanced Vehicles, J.W. Automotive Engineering took over the Slough facility and started manufacturing strictly road going versions of the GT40. J.W Automotive was headed by John Wayer who was the GT40 ex-team manager and Ford’s distributor in England. His goal was to create a more road-worthy GT40 than the production versions made by Ford Advanced Vehicles. This new car was called the GT40 Mark III.

Many external changes distinguished the Mark III. Safety regulations dictated that the headlights had to be raised with circular sealed beams installed. At the rear, the body was extended to provide space for a rear locker. Inside, the interior was fitted with more upholstery and standard seats that did not incorporate the Mark II’s clever cooling system.

The Mark III’s engine was changed to the much more simple 289 found in the Shelby 350 Mustangs. These engines used a four barrel Holley carburetor instead of the Webbers used on the Mark I. However, the transmission and clutch were identical to the race car’s setup.

Unfortunately, John Wayer failed to make a superior GT40. The fit and finish did not match the cars made Ford Advanced Vehicles which were built under a no-expense-spared policy. This may be the reason that only seven or eight were ever completed. Despite these facts the Mark III was still a very capable car that used the same proven chassis and aerodynamics that helped the Mark II conquer Le Mans.