The success of Ford’s Capri prompted other manufacturers to offer similar models. The Firenza coupé was Vauxhall’s effort, launched in 1971. It bore a family resemblance to the Viva HC it was based on, but had more rounded, fastback styling; arguably, it was a more attractive creation than the Capri. Engines ranged from an insipid 1159cc to a rather enjoyable 1975cc, but changes in 1972 introduced 1256cc, 1759cc units, as well as the thoroughly entertaining 2279cc powerhouse of 110bhp. In 1973, the coupes became known as Magnums instead.
info from Octane