A visit to an automobile restorer or even a good body shop would probably be a good start after you go through the links posted by Lori and check by numbers. There is equipment that a modern body shop should have that will tell you the thickness of the paint and a good painter will be able to identify they type of paint on your car to see if its original.
A good bodyman can restore a car to the point where its hard to tell to the average person if its original or not but they can tell.
Many cars in that era had replacement engines (rather than a rebuilt) which isn't a bad thing if the engine checks out to be the right one.
