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The C6.R ZR1 GT2, if you were to use its full name, was the model used in the last four years before the Corvette C7.R was introduced, and had a slick sequential manual operated by paddles that was combined with the rear differential to create a rear transaxle. This style of transaxle eventually made it into the road-going Corvette, especially the Grand Sport and ZR1 of the C7 generation.
The early C4's had their problems, what with the 1984 Cross-Fire Injection and its unusual 4+3 manual transmission. By the late 1980's, the fourth-generation Corvette had evolved into a more desirable automobile, thanks in part to the arrival of the ZR-1. 
This car was created by Doug Rippie. His claim to fame was the Corvette Challenge Series. Rippie loved racing Corvettes in the US, but, his life-long dream was to take on the world-class marques at Le Mans. So, when Chevy introduced the C4 ZR1 the opportunity was opened up. Via his collaboration with MerCruiser and Lotus Engineering, all with Chevy’s blessing, the "Black Widow" program created special street and race versions of the LT5 engine. This engine made 525hp.