 As a result, the new premier class known as GTX (Grand Touring Experimental, which was based on FIA's Group 5), brought on the absolute dominance of the Porsche 935.The 935 became the most successful car in the series.The most successful driver of the 1970s was Peter Gregg, who won championships in 1971, 1973, 1974, 1975, 1978, and 1979.