I have the Flex-a-lite 490 (shrouded dual 12" fans) in my 78 C3, with a 540 BB. Temp switch turns both fans on at around 200*, shuts them off at 180*. was using the car as a daily driver, work commuter for years, until retirement. would be stuck in traffic jams, stopped on the freeway, no problems keeping the BB cooled. I'd sit there in the stopped traffic on a 90* day, and just watched the temp gauge cycle from 200 to 180, back up to 200, fans kick on, temp drops down to 180. never any issues or overheating. I did learn a lesson to have the individual fans wired up to individual relays and circuit breakers. the electric fans definitely reduced the stress & worry of driving the 540BB in traffic.
also, Edelbrock alum water pump, Be-Cool radiator. FWIW.