8 1/4 strength

After you upgrade the 8-1/4 with the sure grip and gears, you'll will still be under a 8-3/4 prove tag. There a good strong rear. They can handle 11's in a big block Duster.
That is where I would yeild. Pressing on could, though I do not know first hand, be a problem. Running 10's in a street trimmed car is demanding on parts. The 4spdnis harder on them vs. an auto trans.

IMO, when you say mild, your not running 11's. Maybe high 12's.