Griffin radiator
Radiators often get blamed for poor cooling performance.....when it is other system components that are the problem. Case in point is my GTO. I had a custom made alum rad for it, two rows of 1" tubes. Temp would still creep up on hot days. The ultimate fix was the water pump. I modified the 455 engine to take the SB Chev Edel Victor #8810 water pump. These pumps are not cheap, but when you remove the rear cover, you see why.....
The casting is completely new & where the impeller fits, fully machined with about 0.030" gaps. Six blade impeller; because of the tight gaps, ALL the water gets captured...& pumped through the engine. The pump made the biggest difference. Result is the temp toggles around 180*, under ANY driving condition, even on 40+* C days. It actually cools down slightly at idle.