This is one interesting freight car. I've been browsing images on-line of these B&O wagon-top cars lately, and noticed a variety of lettering and logo styles on them. Whichever one is ultimately selected, the car is going to be a great piece in the collection.
Why not put a different logo/lettering style on each side? As long as the background color is the same, and the style was used on the car at some point in its career, both sides would be correct, but different. No one would be able to see both sides at the same time anyway. It would almost be like getting two cars for the price of one.
REPLY: I have seen folks do that on their home layout, somewhat of a model railroader mentality. I think our primary mission is to preserve history, and in most of the departments that is the overriding consideration. For your suggestion, our car may have never carried one of the other schemes, as there were many variations, Then do you paint a fantasy number on the side with the made up scheme? Who knows which is history preserved vs history being rewritten?