I don't have any experience with 300s but out here the 250s burn intake valves (!) before exhausts. Some blokes drill and tap the heads for a top water outlet and claim it helps valve life.
I've done a few 302/351w F150s from the early 90s that blocked cats after a head gasket failure - coolant always kills cats. They all burnt out #8 exhaust valve,and the customers complained of a hot l/h floor.
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