Who said 540-hp was enough to satisfy everyone?  Chances are if you opted for a Shelby GT500, you’re power-hungry, and someday you’re gonna look for more.  Without even opening up the motor, you can unlock 612 rear-wheel horsies on your beast.

The mods will cost about $5900, and more like $8200 installed.  But don’t you want 621-rwtq ripping your pants off?  Just slap on some American Racing full-length headers at 1 7/8 inch with a 3-inch crosspipe, a Magnaflow after-cat 3-inch exhaust, C&L cold air intake, a larger single blade throttle body, C&R heat exchanger, Ford Racing 3.73:1 gears, and get a custom tune.

2007 Shelby GT500

Some shops have clocked the aforementioned mods at the track at 10.43 seconds in the quarter-mile at 133 mph, using a 2007 GT500 strapped with drag radials on wider-than-factory rear-wheels.  Parts $5869, installed $8169.  612 rwhp and 621 rwtq.  Nice.