Transfer case difference?

I'm looking at doing a regear to the transfer box and was thinking it makes sense to have a spare case to regear then I can do that on the bench while still being mobile. This is then leading to the next question, in the current absence of a electric automatic donor box are there any physical differences between the manual and automatic cases either in the actual casting or in the drive train? Obviously the actual ratios are different but they will be being changed. I ask as there are different gear sets listed for the 2 different transmission types with my automatic already having a 1.3 high set and the proposed set being 1.5 I don't want to find out the expensive way that I have bought a donor that won't work.