A cast iron crank is not as strong as a steel crank. But cast cranks are more forgiving about balance and vibration problems. A steel crank will take more rpm/horsepower abuse. Most 402 two bolt motors are cast iron cranks. To tell the difference, look at the front of the crank from the main journal to the rod journal down the center of the arm will be a line that sticks up. If the line is only 1/16"-1/8" the crank is iron. If the line is 3/8"-1/2" and looks like someone took a grinder across it. It is steel.