Dave,
I am not an expert on Ohio Pass as I have only been across it twice and missed the wall the first time. But from what little I know. Just beyond where you end the red line a road splits off from NF-730 to the right, this is the grade. If you look above and a little to the right you can see the wall. The grade then goes on to the left and ends in a meadow to the left of the road a little ways south of Floresta. Remember this was just grading, I don't know where the rail ended.
I am attaching a picture of a sign on the grade just below the rock wall.
Ken