[vettestr]

Cougar958
If engine was balanced in current state and there is NO ISSUES you need to resolve then dig out your old balance ticket. It has a list of all the individual weights that made a balanced assembly. The combination of a rod, piston, rings, and bearings added together are the BOB WEIGHTS that is then hung on the crank and spun up to find the counter balance needed on the crank/crank, flywheel and front damper. one is for internal and the other is external bal. The factor of big end or small end of the rod also determine reciprocating weight.
If you need to replace 1 or 2 pistons etc.. on a balanced assembly all you need to do is replace with the same total or BOB weight and the engine is still a balanced assembly.
If you replace all or 1 of the piston assemblies and the weight is more than 2 grams different (many have different allowable standards) the engine is NO LONGER A BALANCED ASSEM.
Engines will go through 2 extreme or maximum harmonic vibration RPM ranges. An engine that has been balanced has had those 2 extrems moved to a RPM that is for the first below the useable and the 2nd above the useable RPM range of that engine. Unbalanced engines have a much smaller deviation or window where they go through those 2 extreme ranges and both will be in its usable RPM range. This imposes additional stress on the reciprocating assembly and the amount is relative to amount of imbalance.
In short, buying better quality products and then ADDING extra stress by not having them brought back to even the factory (much less strict) standard is not how you built everything else I'll bet.