The cross-plane V8 was used in the FIA GT Championship after Le Mans.
Edit: A total of 2 CLK-GTR's were built for the 1997 GT1 Championship and a third was added later on. Each of them had a V12 engine in the beginning. In 1998, 2 of them competed in the FIA GT1 Championship and the third, Chassis #5, was pretty much a spare I believe. At Le Mans, the 2 cars that had competed in the FIA GT1 Championship from rounds 1-3 had their aero changed and received the C9's engine without the turbos, subsequently turning them into CLK-LM's. After Le Mans, I suspect the crankshafts were changed from cross-plane to flat-plane, which would explain the different engine note. Aero upgrades put onto the cars for Le Mans stayed on them for the rest of the GT1 championship.