He moved back, at last, to IMSA racing in 1980. He would drive a Datsun 280ZX which was updated to the latest GTU specs. The car was fitted with bigger tires and was lighter, it was given gor 270hp. At the end, it was a totally new challenge, but he had to face a much more stronger opposition than in C Production. The Mazda RX7s had entered the fray and had clearly become the class of the field. Drivers like Walt Bohren, Lee Mueller, Brad Frisselle, Roger Mandeville, Jim Downing and Jeff Kline were all very skilled and professional. Paul Newman garnered some good results but no victory at all.

For the 1981 season Sharp, in partnership with Electromotive, decided to escape GTU and the Mazda's and move up to IMSA GT class for cars over 2.5 liters. With a Nissan President 4.5 liter V8 engine and the work of Gene Crowe and chassis designer Trevor Harris, the two teams developed a couple of unsuccessful turbocharged ZX's. They had the power, but the engine design lacked strength and cracked under pressure. The IMSA now shifted focus to allow even more highly modified prototype cars that outclassed even a 700 horsepower twin turbo V8 ZX. The project was abandoned.