Interesting discussion, and a very intriguing photo of a mystery caboose Bret.
From what I remember from photos and stories, the plow was modified at some point. They went from what seemed to be a plow that was offset on the point, to later a plow with the point on the track centerline. With the modification to the centerline, I think more bracing to the plow body was added. I seem to remember Elvin saying they had scrap in the body; I believe he knew because the OLC occasionally borrowed the plow in the late 1930's to plow the Middle Fork. For some reason, I have the memory of him saying you had to step over chunks of rail, frogs, etc. to get from the front to the back. I know the OLC at some point had their own plow (a flatcar with a Cat blade on the front?), but maybe they preferred the SVRy plow?
Seeing that fairly early photo of the plow behind the high-cupola caboose, do you think the plow was originally built by the Utah Northern? Bret, Jim, Taylor...anyone?