Okay, you made me take a look at the DAT file.
Yes,
NSS_Uboat7c_coning,
NSS_Uboat7c_deck,
NSS_Uboat7c_hull
are the ones you need to chnage by replacing 7c for 41.
Turm7c_5, 6,7 are different conning towers for AI VIIC/41:
Turm7c_5 is with one AA gun;
Turm7c_7 is with two AA gun;
Turm7c_6 is for U-flak boat.
It is easy to find out what Turm belongs to what by looking at the EQP file.