Thanks for your comments guys; I finally got around to looking at the head (photos attached). It seems that the small semi-circle is where the exhaust (smaller) valve lives. The spark plug and the intake (larger) valve live in the main hemispherical chamber.

Does that head seem repairable? Some of the valves looked very corroded, but I am not sure if it's only surface corrosion.

Is the CR 9.0:1 on this motor? From the head part number, does anyone know what year vehicle this would be from, and the horsepower (USA motor with air pump)?

If the M130 weighs 450 pounds, the head with manifolds, carbs, and cam must be about 150-200 pounds of that. Man, that thing was heavy!