It's also worth pointing out that while you have it split change the shaft seals, the one on the main shaft behind the engine clutch and the one that separates the hydraulic/wet clutch oil from the transmission/rear end oil. Also, there are three pilot bearings that should be changed. The one in the engine flywheel (ball bearing), the one between the main shaft from the engine clutch and the transmission input shaft (bronze), and a cage roller bearing between the transmission and rear end. I went ahead and changed the three main shaft bearings, all the same. I was dumbfounded to find that they are metric!! I wouldn't have expected to find metric deep groove ball bearings in a U.S. tractor from the early 50's.
It's been a few years since I had my hands this deep so I might be a bit off on my descriptions. Feel free to correct me.