Also, the cast crank 340 balancers are not the same as the 360 balancers. Just some FYI. What's your intended power level? I ask because the cast crank properly prepped and balanced is good for 550 HP maybe a tick more. They are a good bit lighter, too. Just a thought.
This. I have a cast 340 crank that is internally balanced. They do not need near as much to neutral balance as 360 cranks do. Unless your using forced induction or laughing gas the cast works just fine.