The big problem in todays world is that almost no one balances an engine any more, since pistons are within a couple grams and rods are within a couple grams, most of the companys only balance the crank shafts, useing the nominal weights of the rods and pistons, there fore the cheap $100.00/$150.00 balance jobs. A few yrs ago i bought a rotating assy from Shafiroff, and crank and rods came from them and the pistons were drop shipped from JE. Pretty good indication that they only balanced the crank shaft.
JMO
Zip.