For 1978 the Concours was discontinued to clear the way for the newly downsized Malibu, and the Nova Custom inherited much of the Concours' exterior finery but lacked the stand-up hood ornament displayed by the Concours. Upholstery choices included all-vinyl or Edinburgh woven sport cloth/vinyl. More basic versions of the 1978 Chevrolet Nova had the same grille used in '76-77 and added a gold-tinted Chevy bowtie emblem at the leading edge of the hood. For '78 Nova was also available with Rally equipment, which included yet another front-end layout: a diamond-pattern grille with horizontal parking lights and black headlight bezels (basically the '76-77 SS grille), plus triple band striping and color-keyed Rally wheels. All Nova drivers faced a new dual-spoke, soft vinyl-covered steering wheel; the same one found in the Caprice and Malibu.
Any 1978 Chevrolet Nova could be ordered with a 250-cubic-inch six-cylinder engine, a 145-horsepower 305-cubic-inch V-8, or a 170-horsepower 350-cubic-inch V-8. Law enforcement agencies in 48 states were driving Novas by now, as the sales brochure boasted. Production dropped almost 100,000 for the model, to 288,000, making Nova the only Chevrolet series to show a sales decline for 1978. Sales of the Nova hatchback body style lagged well behind regular coupes and sedans, and base models handily outsold Customs.
Upon introduction of the downsized GM A-body (later G-body) mid-size cars in 1978, the X-body and downsized A-platform had similar exterior dimensions. The roomier and more modern downsized A-bodies outsold their X-body counterparts.
Source: Wikipedia, 2014