Without dash plates or other ID imprinted on the car, it’s hard to tell some of them apart. Classic Roadsters are the most identifiable due to the step located in front of the rear fender where it attaches to the running board that does not appear on other models. I have looked at a lot of photos both here and other places on the web and I can see some differences between the models. Some differences relate to type of taillight, type of head light mounts, and whether the front fascia is split or not. I’m sure other differences are easy to spot when you own a certain manufacturer’s model.
I’d suggest you start looking at the photos here in the gallery and see if you can find similarities. Maybe at some point someone here can publish a short list of identifiable differences. It might be a good project if someone attends a TD replica event and could take some notes or photos.