cast iron water pump vs aluminum pump

radiator is a new aluminum 3 core 22" champion, and cooling system is clean&green, is anybody running a cast iron pump with a built 340 and if so what is the diameter of the crank & water pump pulleys? My car has a 5" crank pulley and 7" water pump. I was wondering if someone put an underdrive pulley system on this engine or if its stock?