Unfortunately, each of those 4 pictures is a different corner of the block. Both left and right heads, front and back. It appears to be coming from the head to block mating surface on all four corners. The block is a marine engine from 1995 I think. I don't have the casting number off hand but I can get it. I had a machine shop go through it and bore it 30 over due to some rust from water sitting in one of the cylinders. It's a good shop and I trust their work. They decked the block and heads for me so there should not be any warpage to worry about.