you have some room for error.
the bearing surface is much wider that the actual bearing, so no problem there.
the other issue is how the brakes, drum or disk, align with the backing plate or bracket.
if you get the axle a bit too long shims can move the brakes out to match it.
cutting the axle too short would be a bad thing.
I would remove the diff pin, then install the axle in the housing. assemble the brakes to set the outer part of the axle properly, disk centered in the bracket.
then measure the gap between the axles center ends to see how far you will to push the axle out to clear the diff pin.
the C clip sets how far the axle can go out, the end of the axle hitting the diff pin stops it from going in.
both of those gaps have some play.
EDIT:
OK, just reviewed the info and realized I gave you info for a regular diff, not a Torsen.
so replace "diff pin" with the Torsens center spacer.
same procedure, put shaft in, assemble brakes, look at gap between axles, shorten as necessary.
since it's a Torsen, look at the wear marks on the old splines to see if you have enough room to cut it off.