Cobra. Viper. Both snakes, but neither on a plane. It’s this striped serpent from Ford that might have the Dodge Boys’ panties in a bunch, since it’s putting 500 horsepower to the rear wheels from a supercharged 5.4-liter V8. Yeah, so what, right? Trouble is, the 2007 Ford Mustang Shelby Cobra GT500 is expected to start in the mid-$40,000s, about half the price of the Viper. If for no other reason than to save face, the 2008 Viper needs more power.