I understand this, the holes in the ring gear are 13mm, and the holes in the lsd unit are 12mm.
You obviously can't put a 13mm bolt though a 12mm hole, but you can put a 12mm bolt through a 13 mm hole.
If you had some sort of spacer that was threaded on both ends to essentially make your 12mm bolt, 13mm for the part that goes through the ring gear.
Would that be possible, or would the spacer be far too thin and just crumble?