Mark, Based on what you have described your lay out to consist of, 1850 cfm is not enough to cool you at idle with no road speed. The two main factors to consider are coolant flow rate and air flow. With no or near zero road speed conditions. 2,500 cfm is the smallest you want to go for V8s (up to 350 hp) with 2700-3300 cfm better suited to protect larger HP motors. Look at SPAL fans, high quality reasonably priced, and they have data to back their fan specs. Use the largest puller fan or fans that cover as much of the core area as possible. COOLANT FLOW: You can't have too much gpm's of coolant flow rate at idle, period. What governs this is radiator tube/core design and water pump flow rating. Once you are moving enough air through the core at higher road speeds, if your radiator and water pump flow rates are OK, the fans will not be needed. The fans should be thermostatically controlled to turn on/off at temps near 180-185. Dont forget to check the voltage drop at the fans to make sure your are providing the max voltage to the fans, otherwise they wont flow the air they are rated at. Even 3,300 cfm fans means nothing if fans are only getting 10 V.
If you are running 160-180F at higher road speeds your coolant flow rate may be adequate with the cast iron OEM pump but you may benefit with a water pump that has higher gpm flow rate at low speeds. Your pulley ratio is OK based on sizes you mentioned for street duty. Stewart coolant pumps have a good reputation and flow charts are available for their pumps. Be careful of folks selling hi flow pumps with no flow chart data to back their claims, same goes for aftermarket elec fans.
All, I learned alot from these articles, clear and NO BS, pretty accurate. Very helpful.
http://www.streetrodstuff.com/Articl...g_Suggestions/
http://www.streetrodstuff.com/Articl...g_Suggestions/
Bill