Looking to buy/build 500-600 fwhp 360

I think I'm going to end up about 550 hp as my elevation is 3300 feet. It looks like a cast crank will hold up at this level especially is everything is well balanced. I remember reading the 360 cast crank is larger than the 340 crank and the chevy 350 crank. Crowers website talks about their forged cranks being used in very high horsepower applications.
So, any reports of broken cast cranks at this horsepower level? I'm talking about keeping the RPMs under 6500.