That looks like a 3-71 Detroit. The 2,3,4, and 6-71 all had interchangeable parts minus the blowers, blocks and heads. They could be configured numerous ways. For example, the blocks were the same on each end so you could have the blower on whichever side you needed it. Really cool and simple design. Even had some that laid over like the slant six Dodge engines. They weren't the most economical diesels to run but, they were dependable and easy to maintain. The Navy had tons of them simply because of the ease of keeping parts on hand. The Detroits were my primary job, three of the five years I was in the Navy. Had lots of fun building and blowing some up.