Hennessey Performance Engineering strapped founder John Hennessey’s 2018 Ford GT Heritage Edition to the dyno to see just how powerful the supercar really is. The GT laid down an impressive 581 rear-wheel horsepower and 513 pound-feet of torque. The GT’s twin-turbocharged 3.5-liter V-6 engine officially makes 647 horsepower at the crank, which…