New player, dumb question?

[PretzelDarter]

Hello!
I'm planning on playing SH4 soon, likely with the Fall of the Rising Sun Ultimate mod (and perhaps some extra little mods on top) but something I've been wondering, and haven't really figured out a real answer on from what reading I have done on the forums and other places, is whether or not all members of a given submarine class exist in career (mostly concerning Gato and Balao classes, as earlier boats seem to pretty clearly have sister-ships represented from what I've seen). I'm assuming they do, but I'm also curious if there's any real way to pick a particular one (I'm aware of how the upgrade system works, I think), probably through some file manipulation (I swear I remember seeing a mod that would do something like that here via temporarily removing every other playable sub but I don't remember where I saw it). Anyone got a clear answer or insight into this? I just wanna play my favorite individual fleetboats like Wahoo or Drum, or other ones I find interesting