With a little more power, a less weighty engine and new performance upgrades for 2011, the folks at Ford's SVT performance unit continue to turn the once portly, push-pig Shelby GT500 into an ever-more-legitimate all-around performance car.Like its V6 and GT brethren, the GT500, which the company is to unveil at the 2010 Chicago Auto Show, gets substantial upgrades for 2011, only a year after a major overhaul for 2010. You can think of it as a preemptive strike against the Camaro Z28 that has long been rumored to be waiting in the wings at Chevy.