Not 100% sure, but it looks like a Clay Smith Cams decal. Wish I still had one! Beautiful car and a great story. That garage looks full of very nice toys!
It is a Clay Smith Cams "Mr. Horsepower" decal. The Thrush decal was inspired by the Clay Smith version, which dates back at least to the fifties or even earlier, the company having its origins in the thirties.
