Getting pretty tough to tell on a lot of these things - you need a scorecard to "grade" them. All the correct parts, but the side of the case is awfully shiny, with an apparent lack of turning operation feed lines, plus the "step" where the distributor cap fits down onto the top appears almost nonexistent (which could indicate the case had been turned down, and restamped). In the long run, I think you should assume the worst in almost all cases - there are just too many people trying to cash in on rare parts and high prices.
I have a bonifide original, unrestored 499 that my best bud scarfed for me in a local meet a couple of years back for next to nothing - that's a great indicator that it indeed was an original - a counterfeit artist or a Camaro/Chevelle enthusiast would have known what it was, and the price would have been out of this world either way. My thought has been to trade it straight for an earlier date to fit my Dec. 68 L78, but the longer it goes, the more hesitant I am to ask someone to trade it for fear I'll get the king-size salami in the trade. I truly believe the only way I can ever accomplish it will be to send it to Jerry to restore, authenticate, and then act as a middle man to broker the deal (so he could verify both). Not having ever approached him about it, I won't assume that he would do it, but at least he could restore a couple more to add to his wallet.
BTW, I tried to trade the 499 to one of the eBay sellers we have been talking about, thinking he had an original, but when he saw the pictures of mine he actually declared mine to be a fake. I got a good laugh about it, plus resolved not to take this guy in any casual consideration as legit. Shame there aren't more honest people than there are -