Hi Bill.
Just split the nut, or grind it off, you are not going to want to save the shaft anyway. The 101 has a left hand thread screw there. Later scout shafts had an extension into the oil pump, with a left hand nut on it. It was common to use these when 101 shafts weren't available and just cut the end of the shaft off. That looks like what you have there.
The pinion gear is a press fit on the shaft, so it is best to use the correct puller on it, and maybe a little light heat, once you have the nut removed.
This process is a lot easier with the crankcases together. Take care not to put any weight or pressure on the rhs case, as it is easy to damage the housing around the captive thrust washer .