I've driven the route several times, both to follow the still-existing standard gauge rails, and the highly-degraded roadbed of the 3-foot track. The last visible n.g. grade fades out just about where Superior comes into view. The book about this short line includes a map, and also shows the only known(?) photo of the narrow gauge, a wreck site. An interesting drive, suitable for SUVs.
For a brief period, both the old n.g. and new s.g. steam locomotives ran the route. Three s.g. Moguls serviced the mines until diesel came on line. I believe this was the last short line in the US to run steam. One of the Moguls is on display in the (Scottsdale) McCormick-Stillman Park.