[jhv48]

As I understand it, California will honor the registration “as is” from Montana and all you will need to do is go to your local California DMV and do a simple transfer of registration. Then your car will be registered as a 1965 Shelby cobra in California.
But, here’s the catch. Since your car is not “really” a 1965 Shelby Cobra, you can be charged with fraud and your car impounded if caught. And that’s a big “if”.
Many a replica has been (and still are) registered as 1965 cobras in California. Most are rarely driven so the chance of getting caught is minuscule.

If it were me, I would go the SB100 route as stated above and not complete the sale until the registration process has been completed.

If you’re a gambler, just transfer the car to California and fugetaboutit.