We did this tour beginning on the north bay at Larkspur. You could park your truck camper there easily. Our daughter, who lives in San Fran, did the tour with us and even she was highly impressed.
We took the ferry from Larkspur to Fisherman's Wharf where we got on the tour van. It returned us to the wharf at the end of the day and we took the ferry back to our vehicle. The tour gave us all the major highlights of the city and included a lunch stop in Sausalito and the Golden Gate Bridge. We had time to walk through the Japanese Garden (May was perfect for blooms).
San Francisco Small Van Tour