I would think that the diff still needs to be supported (by a jack) while crossmember (diff drop) is replaced and may also be needed to adjust the height of the diff to align to the new crossmember. But I have not done mine yet and can't speak to it specifically or knowledgeably.
There may technically be room, depends on tire size as well.
What I would suggest is to watch a few YT videos about installing a diff drop on a 100 Series, I know many exist (Got a few of them bookmarked) and they may give you a good enough sense of the project and it's requirements to answer your questions.