Back to my idea of creating a level playing field based upon value..............
One fair way would be to take the Market Insurance Value of a car.
Show us your Insurance Policy and categorise your car to the pre-determined market range i.e under 50k etc etc
1st, 2nd, 3rd for each class and then an overall winner based upon People's choice.
Judging would still be based upon the existing criteria i.e. paint / engine bay etc etc.
Only a thought