The 641087 casting number is one of the more common for the L-134. Late 2A, 3A, replacements, welders, and I believe, some Wagons, and some Jeepsters have this casting. I believe the "W" stands for Wilson Foundry. The 3 or 4 is the cast form number.
Because the serial number is gone it may be difficult to determine the original application for these engines, but you might be able to date it. There might be a date stamp on the edge of the engine surface...where the oil pan mounts.
Tim