Balancing an engine

The big thing that needs to be considered is way back when that crank was built/balanced and kicked out the door standards ie. gram/inches tolerances and the machines used to do the balance have changed alot compared to todays standards and equipment accuracy. Maybe not considering what the factories today still kick out but the aftermarket world has improved a lot. Basically in most cases cranks today have improved with the advancements. I had a 440 crank check balanced 2 years ago and you could tell this was a stock crank, hadn't been touched since built and the balance was out to lunch by todays standards (hell probably even 60's standards).

Quick answer, getting it done is cheap insurance.