The 230 (251?) engine shown appears to have siamese intake ports, where each new separate intake casting feeds 2 adjacent cylinders. From the bolts showing it looks like the 3 castings differ slightly.
Just a guess: he probably used a rocker arm from some existing engine by planning his positions carefully. There's probably a fitting you can't see that takes oil from an external source (pressure switch, filter?) and feeds the rocker shaft, etc.
Here's the "Riley" Model A head in section
