Stephen,
It looks as if Richmond Gear is still making them in the 3.54 ratio - and lots of other ratios, and Summit Racing (among others) are selling them for under $200US.
Look here:
https://www.richmondgear.com/auto-pa...ing-and-pinion
It wouldn't be a surprise if you found a Richmond Gear outlet down under...
The ring and pinion may fit OK as is, or it may need Dana 44 ring gear bolts which are a little different from the Jag - it's been too long for me to recall, but Richmond could likely clear that up for you.
I think you can probably find some rebuild parts for the PowerLok too (DuckDuckGo is your friend).
Hope this helps,
Tom