I had a stock GM crank in a 355 SBC that lasted 7 years before splitting into halves

Plenty of racing (over 1000 passes), about 50,000 street miles. I wasn't upset. Aftermarket cast cranks are usually rated to 500-550 fwhp with forged uping that # by a good bit (800-1000 fwhp). All depends on what the engine will see for abuse and times it gets abused.
Derek