IMHO:
There are a lot of very good answers here. Let us go back to basics. Of the Big Three, Chrysler balance jobs were by far the worst. That wasn't by accident. Chrysler engineers put a lot of thought into the difference between good and good enough. They knew how far out things could be without getting complaints from the consumer. They were, of course, building cars to sell. They were not building exotic pieces of engineering art or future collectibles. Never once in my childhood did I hear Mopar engines described as rough running.

Now stop and think of the hundreds of millions of engines rebuilt with "stock replacement" parts. Do you think they got balanced? Not on your life. Yet we don't hear about rough running rebuilt shortblocks.

So what if one rod throw is tapered and needs to be taken down 0.010"? Change in weight would be 19.4 grams, minus the extra weight of the thicker bearing shells. It would indeed be inconsequential. If all the rod throws were reground it'd be even less of a change.

Any tiny amount of metal that might need to be removed for fitting is well within modern tolerances, and the factory tolerances are much larger. Modern balance jobs are probably to 1/10 the tolerance of the factory balance job.

If I bought a 440Source rotating kit I'd pay to have it balanced. If my engine assembler wanted to do it again it'd have to be on his nickel.

Finally, we act as if the formula for balancing the rotating/reciprocating assembly of a V8 was handed down by God Almighty. It wasn't. There is no mathematical derivation from which the formula was developed. The formula is based on empirical data. If it was based on analysis, such things as overbalancing or underbalancing the engine would not exist.

Best Regards,
R.