The owner is a friend so I only have the picture.
What I can see in the picture is not cast together with the block, so not part of the block.
If you zoom the image, it appears that the "pad" is attached with 4 screws.
The cylinder head is from a B engine.
Do you have any more pictures? Is this engine running a welder? Air compressor? Generator? Buzzsaw? It must have been used in wintertime, what with the priming cup added on.