Been following this thread for a while now. I'm working on a cooling problem as well. With just the original 4-row Griffin radiator and a 16" high wattage fan, the car can peak out between 235F and 240F when stuck in rush hour traffic (air temperature 87F). I added an HVAC aux heat exchanger and a 265 watt fan in front of the Griffin, tapping off the thermostat bypass line and returning to the inlet of the water pump. Hose diameter in this section of the system is 5/8" ID. Peak temperature in traffic is now 225F. An improvement, but I'm looking for 210F max. I'm soon to install a fan cooled
oil to air heat exchanger. If I get a 5F drop, I'll be happy.
Now, to my "educated guess" with regard to big block engine cooling. You cannot follow the same rules you'd follow for a small block or a standard sized FE engine. 460 cid or larger engines will always require much more BTU removal capacity.
That being said, if I am unable to reach my goal of 210F (max), my plan will then shift to installing another "regular" sized radiator, to replace the HVAC aux radiator. I"m thinking it'll be a 3-row. It will tee off my main radiator hoses using a 2" tee and a 2 1/2" tee. I'll install a 16" high wattage pusher fan at the front of the car. So, the car will end up with two "full" radiators, one 4-row, and one 3-row.
No more messing around.