Work has continued over the last couple of days with the re-assembly. First the differential was replaced. I ensured the filler and drain plugs were removed (because this would have been an ideal time to "unstick" them if they had corroded in position) and then cleaned up the housing face.
I then coated the face with sealant, lifted the differential into place and bolted it up.
As you can see from the pictures showing the "orange" springs, I was supposed to be creating a lift based on 3" (or 75mm) components from Trailmaster. However I must have accidentally sold the shocks I had put aside. Therefore for now I have fitted a pair of Rough Country N2 which I still had around from when I sold them.
So a miracle occurred and I did some more work on my Jimny today. First of all I repaired the ARB air locker tube that had been damaged. The threads had been pulled out in the brass mounting so I had purchased a repair kit and refitted the fitting.
You can see the original damage in this article - https://www.bigjimny.com/index.php/bigjimny-blog/problems/entry/812-arb-air-line-repair and the photos below show the new parts alongside the old.