I'm not a fan of the BDR shape, but their many customers seem quite happy. If I were to build a modern interpretation of a Cobra with up to date steering, suspension and brakes (sorry - I just can't bring myself to do the dual padded roll bars

), I would go all in with a modern power plant as well; and in that case, there is no better choice to me than this:
The Corvette Z06's Supercharged LT4 Powerplant Now Available as a Crate Engine - Corvette: Sales, News & Lifestyle
Smaller, lighter, more potent and just plain better than the Coyote, it's a no-brainer. Carroll Shelby had no engine brand loyalty hang-ups whatsoever - so why the heck should I?
