Run Silent, Run Deep Campaign (RSRDC) adds about 50 new ships to the game. It also tries to follow the historical convoy patterns/routes of WWII.
There are three versions:
For a stock game choose RSRDCv550
For TMO 2.5 choose RSRDCv502
For RFB 2.0 choose RSRDCv575
There's an "RSRDCv5xx_Patch1" that must be added to any of the above versions. You'll find them through
this thread.