2006 Mustang Shelby GT500 Power and Performance The 2006 Ford Mustang Shelby GT500 was a game-changer in the world of muscle cars. It had 500 horsepower, the most ever for a Mustang at that time. Its supercharged 5.4-liter V8 engine made a powerful sound, amazing everyone who heard it. The 2006 Mustang Shelby GT500 showed …