Got a new sub, but its the same as the old one

[keith_uk]

I started in 1941 with the USS Grayback SS-208 Gar class.
At the end of my 3rd mission i was offered and took a new sub, the USS Drum SS-228 Gato class.

This new sub is the same as my old one!! Its the one with lots of small port holes in the front of the tower. I'm sick of this sub now.
I want one like my 1/72nd scale model Gato with the extra deck on the front of the tower.
Saying that, i don't think the Gato in this game (in the games museum)that looks like the 1/72nd scale model has the prop guard for some reason. I seem to remember the Gar class in the games museum looked more like the 1/72nd scale model.

Anyway, why is my new sub the same as my old one and will i be offered a sub that looks like this:
http://www.internethobbies.com/re1scusnagac.html

Its June 1942 in my game now. Maybe i have to wait until a later year?

Thanks,

Keith.