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There were several successful attempts to build a convertible ZR-1, most of them by private people. The DR-1 was a GM prototype to test the structural integrity of the ZR-1 chassis when it would be topless. The car was built by American Sunroof Corporation (ASC) for Don Runkle, who was the vice-president of Advanced Engineering Staff, which explains the “DR-1” designation. It was a standard convertible transformed to ZR-1 specs.
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.