[cycleguy55]

There is a school of thought that says you can't really use more than 400 HP in a Cobra - at least for street use.

Regardless, if it was me making the decision using the parameters you've given, I'd go with a 427W build. You'd be able to meet your goals and still have something drivable. I'd also be inclined to go with EFI to better handle the changing fuel/air mixture requirements with changing elevation.