440 duster. Need engine build advice

I dont think the cast crank would be an issue - but - the Speedpro pistons are an old, heavy design. If you run the cast crank with it's lighter counterweights and the heavy rods and pistons, you'll spend more $$ to balance it. Are the pistons mounted on the rods? Are they pressed pin (would be a factory type install rather than bushing the rods and/or just floating the pin)? If they are mounted they have to be dismounted in order to properly balance the assembly. That's risky - it's easy to damage pistons dismounting them. If they are assembled - did you get a balance card with them? I need more details on what you have before I would recommend either crank.