Before the Ford Mustang entered the scene in '64, performance-car enthusiasts were limited to one of two types of vehicles: sports cars or big muscle cars. But the '64 Mustang was a fresh, new hybrid of sports and muscle car that offered relatively surefooted handling and straight-line speed. And what's more, it came with a reasonable sticker price. The Mustang and the Mustang-inspired cars from other manufacturers that followed became known as pony cars; over the years, the Mustang's leadership in the group was rarely threatened. Today, however, when the class is reduced to three players - the Mustang, Chevrolet Camaro, and Pontiac Firebird - Ford's innovator faces its most serious challenge. All three contenders are well-built, offer the latest in safety features and are backed by solid dealer networks. As a result, the principal weapon in this pony-car battle is horsepower. Although the Mustang offers 215 hp in its high-end GT model, the General Motors cars up the ante considerably with a healthy 275 hp apiece in their high-performance versions, the Camaro Z28 and Firebird Trans Am. (Later this year, Ford will offer a special limited-edition Mustang Cobra that will close the power gap. However, buyers will have to pay a premium for the Cobra and there won't be many of them thanks to the limited production.) In addition to the engine, the Mustang GT's 5-speed manual transmission is surpassed by the GM cars' 6-speed gearboxes. But power isn't everything, and there's a lot to like in Ford's fancy horse, judging by the maxed-out $26,765 GT convertible we tested. For many motorists, the Mustang's overall attraction and sense of history could very well outweigh the performance benefits conferred by Camaro or Firebird ownership.