Al: The block I mentioned above also has the oblong diamond in the block same location as yours. All of the early Ford flat head block have two oil outlets, I would assume the first photo in this thread also has two, you can not tell from the photo angle. Ford stamped a lot of numbers and letter combinations in the surface under the intake manifold. The information to decipher some of the codes seems to be lost in a fire at the Rotunda building. The 81A block should have four Welsh plugs in the oil pan rails two on each side, it should also have a flat surface under the intake manifold, where as 41 and later blocks have a raised surface.