Regarding my response above, what are the general feelings of the effect of running the exhaust threw the water jacketing and the effect of the center exhaust passage, both blocking the water flow to the rear cylinders and also heating the water as the two other ports do?
In my almost 75 years, I've heard many story's about block cracking and to always look out for it also, regardless of thermostat or not, they have a tendency to to run hot, under extended heavy loads. Radiator condition and block cleanliness effect all engine types but, the V8 has historically suffer more from it.
I've also read accounts of overheating, on this forum, when running on longer tracks, that would mean higher speeds with more air flow, threw the radiator but, a longer load period on the engine.