If you are in the Midwest we are hosting a MCA National show in Lincoln, NE. July 13th-15th. However the registration dead line is this Sunday. If entered in a Concours class it would be judged on a 18 page 700 point judge sheet by some of the most qualified judges in the country. Afterword you can request your judge sheet and that will provide you a excellent work sheet to upgrade your car.
Only issue I can see there is that he will only find out after purchasing the car. Not the time to find out issues, problems and such. Your not getting the car cheaply. Get someone who knows the cars to give it a complete once over and I'm not suggesting someone that is close but the best you can find. A complete inspection is IMHO and others, a very small investment given the price of these cars, and confirmation, hopefully, of what your eyes and your possible rose colored glasses are telling you
I guess (didn't see it mentioned in a prior post) that you have gotten a Marti report on the car as a starting point.
Replacement work and panel replacement will likely make a difference when it comes time to resell the car - IMHO much more important than how a judging event will react to those findings. If they find it - they will let (or should) you know
Using the judges and a show is sometimes frowned on by some since many consider this a place for only those who have spent the time and effort to prepare a car just for that competition but it has been done many times. It will stand our and be obvious if the car looks like it just rolled off the street.
A prepurchase inspection can take care of all of this and an agreement with the inspector (if you get one of the right ones) you can have an improvement list produced also at the same ti,e.