Here's a shameless plug for my employer, who happens to have a special diecast auction going on this week which focuses on muscle cars and exotics. There are even a few Shelby's and Cobra's crossing the virtual auction block.
Click on the "Salute to Scottsdale" banner on the front page, or type in "Cobra" or "Shelby" in the search field:
www.GoMotorBids.com
We've also got some of the 1/12th scale Cobras in the "Get It New" section.