Well right now I'm running a Griffin 26" radiator, 2 SPAL 12" elec fans with a shroud & the fan's about 1/4in into the shroud & Evans coolant. The pulleys are 6in on the crank & 6 1/2 on the water pump.
The guys at March told me to divide the crank pulley diameter by the water pump pulley diameter to get the ratio. Doing that with my current set-up I get 1.08. If I use what Ron Davis suggest, 7in & 5in., I get 1.40---considerably different & better.
Their theory is to get the water flowing faster through the system so as not to "soak" the water with too much heat, making it more difficult to cool. The set-up is in an A-body so space is at a premium.
As mentioned, most pulley set-ups I see have the crank pulley smaller than the water pump, but I think for a higher horsepower set-up I may actually need to "speed things up" as they suggested.