These regulations would be split into three categories; one for one-off prototypes, one for cars of which at least 50 must have been built in 12 consecutive months and one for cars of which at least 1000 must have been built in 12 consecutive months. Ford’s plan was to build a revised seven-litre car (the MkII) for the out-and-out prototype category (this being split into groups for cars over and under two-litres). Additionally there would be a batch of at least 50 4.7-litre GT40’s that would be sold to customer teams for contesting the Sports category with its five-litre engine limit. Some Ford personnel had expressed doubts about the development potential of the basic 4.7-litre engine as far back as late 1964. Consequently, at the end of that year, the Ford Motor Company set up Kar Kraft, a wholly owned subsidiary intended to be small enough to get things done quickly for the firms various racing activities. With Kar Kraft established, one of their first projects was to modify a pair of prototype GT40 frames to accommodate huge seven-litre Ford Galaxie engines. Work was started in March 1965 with no real thought given to actually racing them that year.

Soon afterwards, Ford made the decision to go ahead with the seven-litre programme for 1966. Le Mans had been the last World Manufacturers Championship event of the year so, wanting to gain as much racing experience as possible with the seven-litre, another experimental GT40 was built to contest the Fall 1965 North American Pro Series. This was a championship for Can Am-style sports racing cars (although Can Am itself wasn’t actually around until 1966) and the GT X1 was Ford’s challenger. It was driven by Chris Amon who tried a host of development parts including an automatic transmission at one stage. Essentially little more than a cut-down GT40, the X1 was too heavy against the out-and-out sports racing cars, Amon using it at Mosport, Riverside and Nassau, his best placing having been fifth in the Times GP. MkII’s had many detail refinements over previous incarnations of the model (most of which were executed by Shelby American), the chassis, suspension mounting points, A-arms and uprights all being reinforced. There were also Koni shocks to replace the Armstrong units used before and rear control arm pivot point studs supported on both ends rather than being cantilevered.

Compression was dropped from 12.5 on the NASCAR version to 10.5:1, the de-tuned 427 also being switched over to dry sump lubrication and a single four-barrel Holley 780 CFM carburettor. A larger radiator with a new header tank was mounted higher on the front bulkhead than before, the net result of all this having been 485bhp at 6200rpm. By comparison, the heavier NASCAR unit gave 520bhp but was only intended for much shorter races. Transferring the massive torque generated by the 427 engine was a real challenge, Kar Kraft conceiving the Ford T-44 four-speed transmission that was encased in light alloy and featured heavy-duty Ford internals. Externally, the bodywork underwent a couple of minor visual changes, the experimental long nose configuration used at Le Mans in 1965 being ditched in favour of a MkI production-style affair. Most of the new features were to be found on the lightweight rear bodywork where engine-cooling scoops were mounted on the cockpit sail panels. There were also distinctive snorkels positioned behind the rear windscreen, the hinged rear shell having a slightly higher profile to accommodate the new vertical luggage bins required by the prototype rules.