How do I tell if my 340 is internally balanced?

I believe replacement pistons have the same weight as the original pistons. Oversized pistons also have the same weight as the original standard sized pistons. ------- Stroker/lightweight/racing pistons are another ballgame.

The photo shows a 1/2'' hole in the last counterweight and a 1/8'' hole in another. I've never seen a factory original crankshaft with anything other than 1'' holes drilled in the counterweights.