The most noticeable differences between the Jaguar XKR-S GT (www.jaguarusa.com) and the XK coupe from which it derives are the former’s flamboyant but functional aerodynamic components: air intakes on the hood, and a carbon-fiber rear wing and front splitter. They increase downforce, while a reworked suspension, revised steering, carbon-ceramic brakes, a wider front track, and wider wheels enhance handling. The supercharged 5-liter V-8 engine develops 550 hp and rockets the cat from zero to 60 mph in just 3.9 seconds. The GT, from Jaguar’s ETO division, is priced at $175,000 and available only in Polaris white with black racing stripes. Jaguar will build only 30 examples for the North American market.