That gen of inline 4s is still being used for a lot of stuff. As you mentioned, marine is one application, but generators and pumps too.
If you do a search for GM 2.5L and/or 3.0L
(vs for cubic in) parts, you may get hits on engines that had sumps front, middle, and rear.
A couple of years back, I was looking at 153s and found that these are kind of ubiquitous for industrial applications.
