rttnblly
the vin number tells all............ get a chilton manual and look it up

jeepster420
Go to the library. Get a book for early GM cars. It will have vin decoders, engine block and head stamp numbers, and tell other indentifying marks to look for.

rkfire
The 2nd and 3rd number of the VIN on a 66 chevelle SS must be 38 to be a real SS. There should be a build sheet in the back seat or front drivers bucket seat stuffing, and this might be hard to find. It shows all the factory installed options, paint, interior etc, in coded numbers.