318-3 Closed Chamber Truck Heads

Gday Pete,
by the looks of the photos & my memory, i think those heads were originally from the Dodge trucks 318's (approx '65-'73 D5N trucks) here in Aus & they used the water crossover design to stop the fuel vapourising, as these trucks were common throughout many country/rural areas, where the air temp can often be over 45^C (113^F).