The 216/235/261 engines are all 4 main bearings. The 230/250/292 engines are all 7 main bearings, and all had 2 side covers. They also all had spin on oil filters on the passengers side.
I don't know how many block castings are made from each mold, but as I understand it, there are several molds used per work shift.
Could one batch have left the factory with the wrong number cast in? Just a thought.
best wishes,
Les
