The turret ring gear diameter is different between the two. As for an A with the early style letter flap opening; I’ve seen some A’s with it as I said. You can mix the two to make an early or late.
I think there was a picture posted on M.L. of the new cupola on a D turret. There are even some pics of the drum cupola on early A’s, but also kinda rare. Also, not every G model had the heater in the rear. Maybe most did; I’m not sure. And then we move into the F and the Panther II.
gary