Essentially every mass produced engine will benefit from tighter engine balance tolerances. This is time consuming so car manufacturers don't bother but every properly prepared race motor gets a lot of attention to balance. In a well balanced motor, a couple of downshift over-revs result in a little valve float but no internal damage. A "loosely" balanced motor may suffer stretched rod bolts which will eventually back themselves out causing bad things to happen.
Just curious,
What guy considers rebuilding an m96 motor that has never considered engine balance tolerances? Of all the possible motors to rebuild, this one requires the most precision and attention to detail north of those crazy Italians.