Well... The San Francisco Maritime National Park Association has
BOOKLETS OF GENERAL PLANS ONLINE, which has a link for the S-26 - but it appears to be the only link not functioning at this time... I was looking for a link on their site to contact them with, or a web master link, but haven't found one yet... Some of the plans are "full", some are only the outer drawings, but some do have the interiors... Seems to me that the S-26 link used to show the interior, but I might be remembering a weird dream...
I wonder if they have something on Facebook to contact them through?...