The dash plaques for the GT 500's may be purchased from Shelby American in Las Vegas. Only the Shelby GT's and GT 500 KR's came stock with dash plaques with CSM numbers. The ones now offered for the GT 500's do not contain a Shelby CSM number but come with your VIN number. Also, I believe you can get one with Carroll Shelby's signature for an additional expense.
If I had a GT 500, I'd get one for sure. They might not be offered forever!