340 Info

OK guys and gals, I need some information on a 340 I've found. The casting number on the block is 2780930, and the casting date is 5-26-72. I need to know is it a cast crank, or steel crank engine. It is a standard bore, as there are no over bore numbers on the pistons. The current owner doesn't comprehend how to tell the difference between the cast and steel crank. All help is greatly appreciated.

Thanks,

Bill S.