So spoke to the diff builder today and pretty much settled on a stage II Kaaz. He will be getting me a price this week hopefully. He is crook so it could take a little longer. The diff arrived today and he said he will make a start on it in the next couple of weeks. I have asked if the diff can be ready in October for me bring back when I head over in the first week of November. I got some info on the Kaaz and you do need to do 10k oil changes but you can just use 140w mineral oil, after about three oil changes within the first 5k, using the recommended Kaaz oil. You need an additive but it's made by Penrite so easy to get. He was telling me about this really awesome Trutrac that's way better than the Harrop but they are stupidly expensive and I think stocks have been out for months as they are US made.
Apparently there is a major shortage on diff parts at the moment, with no ETA on new stock. But I think there is still Kaaz centres still available, well the diff builder believes he can get them fairly quick.