The truth is that many are not number matching, that are claimed to be. Far more than anyone will admit. Hemmings still sells re stamp kits. It got so bad at one point that even the lower 327 hp versions were getting re stamped. One example that sticks out that I know well was my Brother's 68 GTO. This car had a 326, not 400 (easily identifiable by the difference in freeze out plugs), and a turbo 350 (different oil pan) with a single trac. Real 242 GTO, but everything else wrong. Blue with no vinyl top. My Brother wanted a triple black car & had a black vinyl top installed and painted it black. Very nice car. Just not correct. Two weeks after he sold it, it re appeared on eBay now as a number matching 400 with a turbo 400 & a positrac. The guy flipped it for 50% more. My Brother was a little bit mad, so we went down the local FBI office & filed a complaint. They dispatched agents to where the car was & the buyer admitted it was done just for show & no harm done. The case was dropped. Then it appeared at a big dealer and sold quickly for more than twice what my Brother sold it for. I can't help but wonder how disappointed the end user was.