modified to the 1996-spec. The F1 GTR 1996 was the fastest variant in terms of straight line speed - the car hit 330 km/h on the Mulsanne Straight at Le Mans in 1996, which is 13 km/h faster than the 1997 long-tail F1 GTR and even 6 km/h faster than the 1996 Porsche GT1. 1997 With the BPR Global GT Series reformed into the FIA GT Championship in 1997, rules regarding the cars used in the premier GT1 class were altered. Homologation specials like the Porsche 911 GT1 had already proven their worth in the final races of 1996, while newcomer Mercedes-Benz was showing the potential of their new CLK-GTR in testing. McLaren was therefore forced to give the F1 extensive modifications in order to be able to compete against cars that had been meant as race cars first and not road cars like the F1. First and foremost, the F1 required extensive modification to its bodywork in order to gain as much aerodynamic downforce as possible. Although it retained the same carbon-fibre monocoque as the road car, the entire exterior of the car was purpose-built. A much longer nose and tail, as well as a wider rear wing, were designed in order to maximize the amount of aerodynamic downforce, while the wheel arches were widened in order to allow for the maximum amount of grip from the tyres allowed by the rules. Ground clearance was also changed to front and rear, rather than the front and rear clearance of the 1996-spec car. The engine also saw extensive modification, with a stroke reduction bringing the BMW S70 V12 down to in an attempt to prolong the life of the engines, while still maintaining the air restrictor-controlled . The standard gearbox was replaced with a new X-trac 6-speed sequential transmission. A total of ten more GTRs were built, with none of the previous cars being upgraded to the 1997-spec. In order to be allowed to construct cars that were so radically different from the F1 road car, McLaren was forced to build production road cars using the GTR '97's bodywork. These cars came to be known as the F1 GT, of which only three were built. The 1997-spec cars are commonly referred to as the "Long Tail" version due to their stretched bodywork, most noticeably at the rear. At Le Mans 1997, the car reached on the Mulsanne straight. This was