I'm not sure about the trans, but going from an electronic to manual transfer case will require some work, console replacement, and some drilling (for the lever). I don't blame you for wanting a manual case. Electronic cases aren't that much involved and can cost $$$ down the road, if you haven't dumped a good amount of money on it already...just wait. You're best bet with the transfer case is to find a doner vehicle, this way you'll save $ on parts, and you'll be able to use the transfer case from the other vehicle. I can't say for certain if the electronic one will work as a manual version due to the fact that it might not be fitted properly to have a shift lever.
I'm not sure if it would help any, but WELCOME TO RICHMOND GEAR
has some good manual units, OD and non OD. As you have a '91 it shouldn't be too hard to find a heavier duty unit, or at least something that's close and will bolt on without much fuss (new bellhousing, etc).