Interesting, I have an original 81 row crop and it had 28 inch tires on it. Older gentlemen I bought it from in 2010 said that they were the original wheels. He bought new in 1946. have seen 2 other 81 row crops that had 32 inch wheels on them and they were represented as being original.
I would love to get a hold of some manufacturing data from M-H and figure some of this out! Too bad that does not exist..