The NHRA blueprint sheet lists the last three digits of that aluminum head casting as applicable to the 1971 Corvette, 425 horsepower, 454 cubic inch engine. I wouldn't describe this source as definitive since its previously reputable standing has been compromised over the last twenty years (right, Jerry?) but the presence of that number on the list is at least supportive of the earlier information. Value? I would suppose that a 1969 casting date would make them more desirable but then, I don't know how many (if any) Corvettes actually got this casting number in 1971. This is probably one of those instances in which they're merely interesting to most people but absolutely priceless to a few. Obviously, the trick is to find the few.
