Looks like the Toy engineers are onto something by not using a radiator or any transmission cooler, keeps radiator heat loads down. At least on the current Tundra.
/s
I'm going to throw it out there that radiator capacity isn't the biggest cooling limitation.
How quickly can you remove heat from the combustion chamber is the biggest limiting factor.
3 ways, more coolant flow, more fuel, or derating the engine when temp limits are hit.
Given the V6 has smaller available area for cooling, with more power, thinking more fuel and derate become more in play.