[40-A Twins]

I believe the oval boss was used to produce both A and B timing cover configurations post 1932. 1 casting that can be used to make 2 part configurations is more economical for the foundry and the machine shop. When the timing hole is drilled at the lower end of the oval, its in the A configuration location. If its drilled at the upper end, its a B configuration. My Diamond motor timing cover is drilled for A configuration, and I just confirmed TDC when the pin is in the dimple.
Kevin