A 1968 Camaro convert built at Norwood would have prefix 123678N for a 6 cylinder, 124678N for an 8 cylinder. If the VIN shows 124378N (8 cylinder coupe)it is likely the car was re-tagged. There are hidden VINs stamped in the body. The easiest to view is on the top of the cowl under the windshield wiper panel. You may be able to read it through the RH vent grille, otherwise the panel will need to be removed.
William - thanks, that's what I thought per several books I've read. Why would someone re-tag a car? If so, why not find a tag to match a convertible? Does does not have an effect on the value of the car?