In the mid 1970s, U.S. automakers concluded that America's long romance with the convertible was a thing of the past. Air conditioning, air pollution, high-speed freeways, and government safety regulations were all blamed for declining soft-top sales, and by 1976 American Motors, Chrysler, Ford, and most of General Motors (GM) had ceased convertible production. This it was with considerable fanfare that GM announced that ''the last American convertible''--a Cadillac Eldorado--would role off the assembly line on April 22, 1976. Auto enthusiasts rushed out to buy one of the last '76 Eldorados, often paying twice the sticker prize for a car that Cadillac advertised as the ''last of the breed'' and a ''priceless collector's item.'' It was not long, however, before automotive aftermarket firms were raking in big profits installing T-tops and sunroofs to open new American models up to the sun and wind. Detroit was forced to concede that the demand for convertibles still existed, and in...