3.79 Stroke CRanks

well of course a forged crank is better, but i run a cast crank in a light altered, that run 8.20 shift at 6200 , the motor is a 417 ,w5 heads alcohol injected making 700 at flywheel, altered weights 1950, been runing motor for 6 years no problems yet????????? Rpm is what kills a cast crank.