If it is for a Concours show, AACA rules usually indicate a judge cannot go underneath a car or remove parts.
However, unless it is an "open to all" custom part of a show, it takes an actual owners club that is knowledgeable of AACA rules and regulations to publish Concours guidelines.
The Corvair club publishes a booklet of Concours guidelines at the following link to get a flavor of a club's rules.
http://www.corvair.org/pdf/concours8.pdf