I had a few diffs built at Trans Gear and Diff (or something similar, on Mahoneys road from memory) in Thomastown a few years ago. It's hard to tell really whether they did a good job or not, but they could do solid spacers, all of the diffs subsequently worked, they had them ready when they said and I paid a fair price.

So I'd use them again, but I wouldn't say they are the gods of all things diff related.