Only very early 89 cars will have the duracast crank, and it would be quite rare for one to still be running with it. All others are for sure forged. there is no way to really tell without inspecting the crank.
Stock crank will handle more power than can currently be produced by the engine. Assuming the harmonic balancer doesn't fail. No one has managed to break a SC forged crank yet other than due to some sort of failure. Stock rods will fail long before the crank.