Correct harmonic balancer?

dano said

Cast 340 cranks have their own special balancer. There are forded 318 cranks and cast 318 cranks and some are internally balanced and other are external depending on year. Since this is a mismatch of parts, was the engine balanced with the 340 crank? I think rebuilding the one you have might be the best bet with mismatched parts.

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To the best of my knowledge, ALL 318's cast or forged cranks ARE internally balanced, ALL 340 forged cranks ARE internally balanced, ALL cast 340 cranks ARE externally balanced, therefore you can swap a balancer from a forged 340 crank to a 318 crankshaft cast or forged, you can swap a balancer from a 318 crankshaft, cast or forged to a forged 340 crankshaft.

Hope this sets you straight