Porsche 962s were allowed entry in Category 3. To further increase the size of the field, small open-cockpit race cars using production road car engines which were raced in small national championships were allowed in Category 4. Later, ACO announced its intentions to completely replace the Group C cars with Le Mans Prototypes. Two classes were created, with LMP1s running large displacement custom-built engines that were usually turbocharged, and LMP2s using the smaller displacement production-based engines. Both classes were required to have open cockpits. However, LMP1 cars that year were just former Group C cars, some still with closed cockpits (Toyota 94C-V, Courage C32, Kremer K8 Spyder, Porsche 962C GTI, ALD C289 and Alpa LM). At the same time, the IMSA GT Championship announced the end of their closed cockpit GTP and Lights classes, deciding as well to replace them with a single open-cockpit class of World Sports Cars equivalent to LMP1. This formula continued up to 1996, with many manufacturers embracing the LMP and WSC classes, including Ferrari, Porsche, and Mazda. In 1997, the first European series based around Le Mans Prototypes was launched, known as the "International Sports Racing Series". Using classes similar to LMP1/WSC and LMP2, these cars were known as "SR1" and "SR2" by the FIA. 1998 saw the creation of another series of Le Mans Prototypes, with the new United States Road Racing Championship attempting to break away from the IMSA GT Championship. To differ from IMSA'S WSC class, the USRRC named their open-cockpit prototypes "Can-Am" in an attempt to resurrect the sportscar championship of the 1970s. However, the USRRC collapsed before the end of 1999, with the series becoming the Rolex Sports Car Series chose to use the FIA's SR1 and SR2 formula instead. 1998 saw a great expansion for the ACO's LMP classes. Following the cancellation of the IMSA GT Championship at the end of 1998, the ACO allowed for the creation of the American Le Mans Series. This series used the same class structure as the 24 Hours of Le Mans, meaning it was the first championship to use the LMP name. At the same time, the ACO greatly altered their LMP classes. The smaller LMP2 class were briefly eliminated, while a new class of closed-cockpit prototypes was allowed in, known as "LMGTP" (Le Mans grand touring prototype). These cars were evolutions of production-based road cars that the ACO considered too advanced