Seal company catalogs by size
In the above mentioned case of the shimmed sprocket seal boss not addressing the seal: it may just be that a slightly
thicker seal is made with the same o.d and i.d dimensions. This way the seal would fit fully home in the seal bore
yet stand slightly proud of the case enough to contact the sprocket boss once more.
Again I am only taking a stab at this as I can't remember the actual set-up.
I used to have dimensional catalogs for seals, bearings, and such which came in very handy.
And if a found seal is too thick.... it's an easy job to thin it so it does run on the sprocket boss.
Again, I'm only taking a stab at this one.... I may be way off track as I can not see it.