I have an online map that includes this grade at the link below. It is part of my NG circle map. If you click on the Gato button below the map it will zoom in and you can follow it north from there. In Sep I drove the road from Dyke to Gato and back. The big loop near Altura is very visible from the road and the grade comes right up near the road there. The grade is easy to spot in most locations. North of Gato I photographed some pilings from one of the bridge. I'll have to dig through my photos to see what I have. I haven't had time to post much of my explorations from Sept. I figured I might get around to that during the holiday breaks.
Narrow Gauge Circle Map
Dave