[rotorwrench]

All the blocks have the same basic profile at the rear with the exception of the half bell on earlier engines. Even the 8BA block has enough casting there but it's just not drilled for the rods. Keep in mind that the anti-chatter rods are a pre-war thing and weren't incorporated into the 59A block either but can be installed if needed. I probably should say that the provisions weren't incorporated into the vehicle frames since the block does have the bosses there.

Some of the 4-cylinder aircraft engines I maintain and overhaul have only 3-mains. The center main takes a beating but holds up pretty well as long as the engine is always assembled to new tolerances. These are 360 CID engines and they have an aluminum crankcase cast in halves. All the main bearings are pinned on these and the center pin is usually loose by the time they are due overhaul.