To answer the question about how to tell an autoshow car:
1. There was only one color for the auto show cars with only one color vinyl top. Having been familiar with Jerry Johnson I could identify that aspect.
2. Besides the 999 and 888 special paint and trim numbers, the door post serial number should read K530-X followed by a single digit number. In this cars case, it is a 7 which makes sense as it was built in June 1953. Remember, people with pull could get cars special ordered.