Remember.....its not the total horsepower generated by the engine, in this case, your cubic inch/ 610 HP., it is likely that 75-80% of the generated hp propels the car or performs work plus its accessories not all being dumped into the radiator. A cooling system is designed for Btu's not horsepower. Your 610 hp equates to this factor:
Determine the number of HP you want to convert to Btu/Hr. Multiply the number of HP by 2,545 to convert to BTU/hr. So, 610 hp x 2545 = 1,552,450 Btu/hr. This heat exchanger would be roughly the size of the car. And the higher the ambient cooling air temperature the larger the heat exchanger must be. If only 20% of the equilivant hp were converted to waist heat to be dissipated by the radiator, the size would be more manageable. 20% of 610 hp or 0.020 x 1.552,450 Btu/hr = 310,490 Btu/hr waste heat to be exchanged. Most if not all radiator sales organizations always state horsepower not Btu/hr because it sounds better and most buyers like to proclaim their highest peak horsepower produced, mostly for bragging rights, as the peak hp is, in almost all applications, an instantaneous number rather than a average over time figure. Additionally, surface area (fins per inch) of the heat exchanger (radiator) is the most important factor but is not solely detetmined by the tube count or their size, but by many factors, including velocity of the circulated media (coolant)..the faster the better, its specific heat characteristics and the temperature differences between the coolant and the cooling air, and the resultant coolant temperature desired to be achieved. Just a few addition points to ponder. Ask those questions to your proposed heat exchanger supplier.
BOB RENTON