I just spoke with Lewis at Southern Automotive today. They offer a Shelby Block/Edelbrock heads combo now, and you might want to give them a call to see how its going. I believe they just sent one of these setups out to a customer recently.
No appologies needed for owning a GT500. Wow..., that was the first Shelby I ever took a ride in about 20 years ago, and I'll never forget it burning the tires at 55 mph getting on the freeway - with three of us in the car!
See:
www.southernautomotiveengines.com for your combo, they may have some feedback.