Concerning the differences between JD combines,  the 36A I have is a1941 model not long before Pearl Harbor which changed everything quickly after and the war production board dictated what could be built and what materials could be used. I know the galvanized metal went away and I am pretty sure the A model full side hill went with it I have never saw one made after the war my in-laws bought a 1948 36B  and they were on a steep ranch I am sure he would have got a 36A had it been available. My father-in-law had a Case side hill before the JD he HATED it!!!  Liked the JD.     17afarmer  Mike