"Hoof governor" is not a term I've heard before, in 65 years in the automotive business and 30+ years teaching the subject in the public school system. In general terms, holes in pistons happen due to very lean fuel mixtures, early ignition timing, or a combination of the two. Damage to a single piston is almost always the result of a vacuum leak at one intake manifold port. Since the stovebolt engines have paired cylinders that share a single intake runner, I would expect an air leak to cause damage to pistons 1 and 2, 3 and 4, or 5 and 6, depending on which port or intake manifold runner has the air leak. Governors in general are there to prevent overspeeding of the engine in lower gears, particularly in heavy trucks with very low gear ratios.
I'd suggest using fuel gas from an unlit Acetylene or Propane torch to search for vacuum leaks- - - -run the tip of the torch around the intake ports and carburetor base, and see if the engine speeds up or runs smoother when the gas is pulled into a leaky joint. Another source of a lean mixture might be a ruptured diaphragm on a power brake booster or a Hydrovac.
Jerry
