Any significance in strength between stock 360 cranks and the cast aftermarket 360 -
aren't the stock cranks, cast NODULAR iron?
Still cast IRON, not STEEL.
Forged anything is stronger than cast of the same thing, period.
Why ever go with a forged crank? Racing or high rpm, or boost, or heavy Nos. Its not really a HP issue, its end use. Can you use a cast crank in a 600hp engine? Sure as long as its a Street engine. Street engines are totaly different than Race engines. Do you really drive you car on the street like you are at the track, WOT or idle? I think not otherwise you might be in jail LOL And if you actually did, it would have to be called a race engine.
Forged and billet crank flex a lot less under high stress, cast cranks flex a lot. Flex a metal object enough and BOOM it breaks.