The biggest improvement over the 8Ns , other than HP, was the live hydraulics. the 850may or may not have a live PTO, depends on the clutch setup too.
I thought the square fronts were all live PTO but not real sure about the 3000 with the Sherman in it.
The V8 in the 8N was a joke. A 60hp flat head in a 30hp tractor was not a good combination. either the trans or rearend went to shit in a hurry if you tried really working it.