Whether on the test track, highway, or your favorite stretch of mountain pavement, you'll notice a substantial difference in the way the Mustang performs in Shelby GT trim. Given a 19-horsepower increase, you wouldn't expect a huge drop in acceleration times, but we got consistent 0-to-60 runs of five seconds flat, a nip better than the usual 5.1-5.2 seconds for the stock GT. But the sensations make it feel like more. There's a deep, throbbing intake roar from the open-element air filter and wonderful subwoofer noises courtesy of the exhaust system. You'll be driving this thing through parking garages just to set off a few car alarms. The stouter rear gear helps, too; the car launches harder, revs up quicker, and midrange passing power again feels like more than 19 ponies' worth. The Hurst shift cures the stock unit's side-to-side slop when in gate. Baby it, and it feels notchy, but treat it like a precision rifle bolt, and it snaps from gear to gear.
Handling improvements are more tangible. The combination of the decreased ride height (hence lower center of gravity), stiffer springs and anti-roll bars, and 18-inch rolling stock gives the Shelby sharper responses and higher limits. We've not previously tested a stock GT with the 18s, but the unmodified car with the standard 17s pulled a 0.87g grip number on the skidpad. The Shelby GT sticks all the way to 0.91 g. The MT figure-eight time also improves, from the Mustang GT's 26.4 to the Shelby GT's quicker 25.7-second blitz. This number tells us how effective all the mods are, as it synthesizes acceleration, braking, and handling performance. As you'd expect, there's a ride penalty, but not to the point of making the car unstreetable, or even unpleasant. Bumps and road chop are more prevalent, especially on poor-quality surfaces. Also be sure to keep that now-inch-and-a-half-lower front spoiler away from curbs and parking blocks....
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