I discovered after posting, that in fact I did have to pull the axle shafts, but they are free floating so its as simple as pulling on them and they slide right out.
The trouble I have now is that I need the tool to remove the hub nut. There are several different hub nut tools depending on the particular Differential in the vehicle. I have yet to confirm which exact type is installed.
Tool: (from 68-70 shop manual)
J2222 - 5200, 7200 lbs (might be 2 5/8" and also referred to as "1929 wrench")
J0870 - 11000, 13500 lbs (might be 2 7/8" diameter? (OTC 1930 wrench?)
J22343 - 15000 lbs - OTC 1931 wrench?
J7341 - 17000 lbs - OTC 1931 wrench?
Tool: (1971 shop manual)
J0870 - H110 & H135 diff
J-5955 - H150 & T150
I don't know if the diff is original to the truck. So I can't trust the GVW stamped on the ID tag of the vehicle
The diff is a two speed vacuum operated, which I believe makes it a 1971 or later. It appears to be exactly like the one shown in this video:
https://www.youtube.com/watch?v=oAK-3VTCxAY
Anyone know how to ID a diff?
I measured the nut on my diff:
Outside Diameter: ~3.5"
Inside diameter tooth slot to tooth slot: ~3.07" This would be the slots that the teeth of the tool insert into.
Diameter of axle shaft: 1.75"
Based on this, it is not either of the two small sizes listed above. So now I'm checking on the size of the J22343 & J-5955 tools