 Complete the following phrase:  If at least 50 cars had been built, sportscars like the GT40 and the Lola T70 were allowed, with a maximum of 5.0  L. John Wyers revised 4.7-liter bored to 4.9 liter, and O-rings cut and installed between the block and head to prevent head gasket failure, a common problem found with the 4.7 engine Mk I won the 24 hours of Le Mans race in 1968 against the fragile smaller prototypes. This result, added to four other round wins for the GT40, gave Ford victory in the 1968 International Championship for Makes. The GT40s intended 3.0  L replacement, the Ford P68, and Mirage cars proved a dismal failure. While facing more experienced prototypes and the new yet still unreliable 4.5  L flat-12-powered Porsche 917s, Wyers 