I agree A .030 .030 crank will run fine, but why do you want to swap it? A Chrysler nodular cast iron crank will take 500-550 HP. Be honest with yourself. Are you really going to make that much?
He might not wanna change the balancer, vert plate etc. Nothing wrong with external balance, just simpler going internal 'parts wise' especially if he already bought them. Jmo