High-horsepower cars almost always ditch the roof last, because a fixed top holds the whole chassis together under violent power. So when a nearly 2,000-horsepower Mustang convertible showed up at Street Car Takeover in St. Louis and started dominating the small-tire class, the 1320video crew could hardly believe it. Open-top cars making this kind of power are almost a contradiction. See how this improbable build holds together at speed.