That's a very interesting problem. Essentially you are importing a kit car into Greece, but treating it as a factory-built example, so need to have a factory specification to work with. Fortunately there is historical precedent for a factory-built Nova - at least two complete examples were made by ADD for export to Italy and France (the former for the president of ANSA Marmitte exhausts). So I think you should be able to present the factory specification sheet to the authorities and in all important respects it should conform with the car you are importing. I have seen the spec sheet for both ADD and Elam Novas and with the possible exception of Armstrong dampers being specified on the front axle of the latter, there is nothing to choose between them.
Good luck with your import Ryosuke.
Lauren