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The L82 engines used a forged steel crank designed for high RPM use. The larger balancer was used to control the vibrations at those higher speeds. Probably overkill on a street engine, but it had "image".
The base engines used a cast ductile iron crank, had a lower redline, and used the smaller, lighter balancer.
No hijack intended, but I have a '74 L48 on which the outer ring of the HB has slipped. I bought an Australian built PowerBond HB which is 8" and plan to fit it shortly along with a new oil seal. I can't imagine that the bigger HB will have any ill effects on the engine, but by asking the question here, I know I'll get a well informed answer.