Duel Gauge trackage in SF

Someone asked me a question recently about duel gauge trackage on the State Belt Line in the City of San Francisco. I know that in the 80's there were still signs around the Levi Straus Plaza but I don't know where else the duel gauge was. I do know that at one time San Francisco was served by four narrow gauge railroads, all tied to the city by car floats and ferries. The railroads were the North Pacific Coast, the South Pacific Coast, the Sonoma Valley and the Nevada & California Railway.
The questions are; where was the car float dock, how much of the State belt was duel gauged and where did it go in the city?
Thanks, Tom