Stronger Crank? - Stock Forged 3.31” vs. Aftermarket Cast New 4”

IMO the cast is stronger because it's designed for performance from the get-go. It has the larger rolled fillets and while it is cast the material is still decent in most of them. But - if you want that power level, it's going to be more cost for the crank, pistons, heads, and carb at minimum. And I'd also add in money for internal balancing and main studs for the stroker. You will not reach 500hp on stock heads, while you can reach 425 on them. Generally I add about 20% over a performance build for a non-factory stroke. If a stick is what you're running, and you race it, I would go with a forged crank. A cast will work, but a forged will work better for longer and some of the initial cost is offset by a savings in the cost of internal balancing it.