before making alterations closer to production. The basic design changes to Frua's CD design vis-à-vis the 1969 Opel CD consisted of a truncated rear end, modified windshield and less chrome application. Dave Holls and Opel's design team supplemented the design with a small front spoiler, larger grille, higher bumper bars and by prolonging upwards the lower edge of the rear side windows across the C pillar to the rear hatch. Final prototype testing was conducted at the Opel Test Facility in Dudenhofen, in addition to load duration tests by Bitter at the Hydropulseur facility of Baur. The Baur team also engaged in significant development work, which included manufacturing a hard foam mockup. Their role then extended to manufacturing the CD body panels, assembling the shell, preparing interior as well as installing the Opel Diplomat's mechanicals. The Bitter CD was displayed, with great success, at the 1973 Frankfurt Motor Show, where Erich Bitter took 176 orders for his stylish new coupe. However, the 1973 oil crisis led to the cancellation of most orders. Despite this, production commenced later that same year at Baur GmbH. The target of 200 units a year was never realised, and Bitter sold 395 units in total. The purchase price in 1974 was DM 58,400. Total production by year SC The first SC model launched was the coupé in 1979, followed by the convertible in 1981 at the Frankfurt Auto Show and the sedan in 1984. Like the CD, the SC was based on Opel's largest model at the time, the Opel Senator. It remained in production until 1989. Exterior styling design echoed that of the Pininfarina-designed Ferrari 365 GT4 2+2 first shown in 1972, and later marketed as the 400 (1976) and 412 (1979). The SC was powered by a fuel-injected Opel 3.0-Litre in-line 6-cylinder engine of () or a stroked 3.9-Litre version of (). Along with the introduction of the convertible in 1981, a four-wheel-drive version of the coupé was also added. The four-wheel-drive system was developed by Ferguson Research who also offered it for installation into the Opel Senator/Vauxhall Royale. In 1984, Bitter announced at the New York Auto Show that it would enter into a limited marketing agreement with GM to sell the sedan version in the United States, through participating Buick dealerships. By being able to offer a premium European product, GM had hoped to regain market share lost to BMW at