Meet the quickest Harley-Davidson streetbike in history. Until the Pan America arrived, no road-legal Harley had ever offered anything close to 150 horsepower. On its debut, a standard height PanAm “Special” hit 120mph trap speed for Cycle World; that was a jacked-up, wire-spoke-wheeled ADV with a big windshield and Michelin Scorcher Adventure semi-knob…