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The Callaway C7 was a completely new, purpose-built car designed to embody the company’s motto: “Powerfully Engineered Automobiles”, carrying on the visual tradition of design by Paul Deutschman and offered in a limited production series. The C7 was the first complete, bespoke Callaway Automobile. This sportscar was equipped with a carbon chassis, front mid engine/rear transaxle design, 650 horsepower SuperNatural engine.
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. 
To understand why the Guldstrand GS-90 coupe and convertible differ so much, keep in mind that during the course of the C4 development cycle, no ZR-1 convertibles were planned, so the base C4 convertible had to be used in building a GS-90 Nassau Roadster, as it was called. The coupe, however, had the advantage of using the ZR-1 platform right from the get-go.
Chevrolet knows their clientele, and with the 1996 Corvette Collector's Edition LT4, the automaker put together a special package that would entice hard-core 'Vette fans with a unique tribute to the outgoing C4 model. The $1250 option brought unique Sebring Silver Metallic paint, 5-spoke wheels, and, of course, special badges and embroidery. It also received the upgraded LT4 powerplant available in the Grand Sport, and with 330 horsepower on tap.
Chevrolet's introduction of the LT1 in 1992 as the base engine in the Corvette phased out the L98 based Callaway Twin Turbo. Previously, Callaway Corvettes made their increased power through positive manifold pressure; now they made it through increased displacement and finesse. Initially called the CL1 or CR1, they designated the chassis they were built upon. They were based on the pushrod LT1 cars (CL1) or the 32 valve DOHC LT5 ZR-1 cars (CR1).