The Shelby Cobras in question are special cars known as "completion" cars, specifically the CSX3000 series (not CSX4000). These cars were issued with unused competition serial numbers from the 1960s. In the early 1990s, Shelby started remanufacturing the 427S/C models and assigned these numbers to them, selling each car for $500K. This happened at a time when the original Cobras were rapidly increasing in value. However, due to a complicated situation with the California Department of Motor Vehicles (DMV), only a few of these completion cars were built.
It's important to note that these completion cars cannot be legally registered in California. This is because they were not delivered as "component" or "kit cars" like the ones Shelby American Inc. (SAI) produces today. Instead, these completed cars were fully finished by the manufacturer and delivered to customers as complete vehicles, which goes against California regulations since they do not meet federal safety and emission standards.