360 vs 383

I agree with the external balancing, wish they were internal balanced. As for the cast crank, no sweating that. People going 450-500 hp for years and never hurt the crank. Some have taken the cast cranks to 9's in the 1/4 without failure.
Ford Clevelands saw 9000 plus RPM on the back stretch at Talladega and they all had cast cranks.