cast iron water pump vs aluminum pump

sounds like I have an underdrive crank pulley because it's 5" diameter,I sincerly appreciate all the input from all of you, I checked Mancini and Year One they only stock 1970 up pulleys, Anybody want to sell a set of correct ones for my application? I think the place to start here is to get my pump spinning at correct speed and then see if it helps my problem, before I look for another pump. Update I also had the recovery tank snifed for hydrocarbons from cold up to 220 on gauge and none were present, so that should eliminate a headgasket problem. As stated earlier I think mixture is close, and i have experimented with timing from 8 to 14 inital ,12 degrees seems about correct for my cam but I do not what the total timing is, Distributor is also an odd ball it has a GM style HEI cap with internal coil,(never seen one on a Mopar before).