Actually, faster flow is generally better. The greater the difference in temp between the coolant temp and outside air, the better the rad transfers heat. Thus, keep introducing hot coolant rather than allowing cooler coolant to linger.
opposite for the block. Cooler coolant absorbs heat from surrounding metal better than hotter coolant. if you slow it in the rad, you slow it in the block also. Better to have cooler coolant entering the block rather than allowing hotter coolant to linger that is less efficient at absorbing heat energy.
Flow is the answer. I think Scott is on the right track with the pulley and am glad it is available to Pantera owners. If I needed additional cooling capability and had already invested in good fans, a smaller pulley would be a good approach.