how much rad do you need to cool a 426sb

well how much rad do you need to cool a 426 small block. it has a electric water pump , 11to 1 compression eddy heads, hughs cam 1.6 rockers ported heads air gap intake. i want a rad that will cool this monster on the street any help would be great did not have it dynoed but i figure 500-600 would be max hp and its going in a 68 cuda. thanks and sorry for the long wright up.:toothy7: