It is hard to tell a real Town Car from a "made one up from a Fordor Sedan" Town Car replica, unless you look at it from the back. It is pretty easy to make the rest of the car look correct.
Look at these pictures of a beautifully restored Town Car from the back and you will see the distinctive sharp edges of the body and the roof line in the back. If the back of the car does not look like this, it is not an original Town Car.