So, I took a wire brush and cleaned a few spots on the block real well. First picture, I cleaned off that date code and it unmistakably shows a "B" so I'm not sure what's going on there. Second picture, that machined surface behind the distributor has nothing but machining marks. In the third picture, I found what looks like "058S" stamped into the side of the block just in front of the distributor hole.
