Jeremiah-
I have had multiple (IH) 44C and 50C decks with the 'water pump' bearings and no wheels. The parts lookup is using the MTD model number designations (i.e. 359) for the 44C and 50C decks, so it's likely they're just using the same diagram for both the older and newer ones. I would not use the parts lookup to try to determine things like this. For example, they lump the IH 782, CCC 782, and 1711 all into one model. There are small differences between all of those models that you'd never be able to determine by using the parts lookup. They list the 46" deck in there with the other attachments...using your logic, I'd arrive at the conclusion that an IH 782 would have been available with a 46" deck, but as we both know, that's not true.
I'm pretty sure I have a service bulletin somewhere that proves the aluminum housings came along quite a ways into CCC production, but I have better things to do than go dig that up right now.