VINs were first used in 1954 in the US. From 1954 to 1981, there was no standard for VIN numbers, so different manufacturers used different formats. In 1981, the NHTSA in the US standardized the format to a 17-character VIN.
So the problem with pre-1981 cars is there is not a standard for all cars, therefore you have to find out the decoding for a particular car company's vehicles for a given year. Not all websites are completely correct in decoding all of the possible characters. Here is a URL that provides decoding for '67 Pontiacs, which could be a start for you. I will warn you that the 1974 decoding for this site is mostly correct, but not completely correct. I don't know enough about 67's to tell you how correct the decoding on this site is for 67 GTOs. This site says its a 2 dr. Sport Coupe 67 Pontiac GTO, built in Kansas City, MO, with an 8 cylinder engine--so not a clone/tribute GTO based on the VIN.
Jim is correct, the Data Plate can give you a lot more information about the details of the car, like paint colors, trim options, interior and exterior options, etc. PHS can give you a good snapshot of what the car was like when it left the factory.