The Do335 initially released in game had some issue concerning 151/20's in place of 151/15's as I recall, I have no idea if that has already been dealt with. The V13 switched to the 151/20's and should have an armored windscreen, dual rear view mirrors, a larger nose wheel that rotates roughly 45 degrees while retracting and larger mainwheels and their doors . The V14 is the one that introduced the wing mounted 103's. Those last items are, obviously, model changes. The 335 when operating on one engine was also about 50mph faster on the rear engine than the front, 350mph versus 302mph for the A.
...Oh, and the rear propeller should be about three inches smaller in diameter than the front...