I reckon my 414 LA motor is making pretty close to 600, I run a 2 core Race radiator designed as a bolt in replacement for a 240-260Z. It's maybe 22", I have dual fans set to come on at 190 and in all but the hottest days the fans only click on coming down the return road after a pass, sometimes they don't come on at all.

but I run a full time oil cooler from a Freightliner truck and a 9 quart system, I think that helps keep from overtaxing the coolant system pretty well. I'm a big fan of oil coolers