http://blogs.mustang50magazine.com/6563 ... index.html
5.0 Mustang magazine strapped the '10 Shelby GT500 to a dyno recently and came up with 478hp and 470ft/lbs of torque. That means with roughly 15% being lost through the drivetrain the Shelby GT500 actually makes about 560hp at the flywheel! Thankfully Ford is underrating these things nowdays. 5.0 said that they believe that on a good day it would probably would have had another 10 to 15 horsepower. That would mean the 2010 GT500 makes about 500hp at the rear wheels from the dealer lot.
