The stock 401/425 crank and rods are forged. They were often used in supercharged engines over 1000 HP. The cast pistons are the weak link in the Nailhead.
Mickey Thompson made a stroker crank for the 401/425 that you see for sale on the web every so often. I had seen a custom stroker 401/425 made by by King recently. I attached a picture of that crank. It is in the 470 CI range.