This site has general arrangement plans of quite a few US diesel boats:
http://www.hnsa.org/doc/plans/index.htm
A dozen different technical manuals from the late war/early post war period:
http://www.maritime.org/fleetsub/
Here's a goldmine I just stumbled across; hundreds of Bureau of Ships drawings of the
Balao-class USS
Pampanito:
http://www.maritime.org/tech/drawings/index.htm