In thinking about the car judging portion of the event, I referred back to this thread where the general membership weighed in on what works.
I think it's important to only have 5-6 classes and to make sure that different cars win for each category (no car can 'sweep' the classes).
I think the the motor (four or six) is irrelevant and should be ignored.
My Proposed Classes
Best Original Spirit 914 (non-factory engines would be non-applicable)
Best Race 914
Best Conversion Car (non-factory engines)
Under Construction Award
Best Interior
Best Single Modification (this class would judge some custom built part or custom fabricated body panel, etc)