ok, listen
that Mk 26 montana..... I love it, but it aint gonna work.
the Mk 26 is an very light system for it's size, and it is not big either. your ship is going to have:
- excess beam
- excess displacement ( to the extend of your stern (if you fit them at the stern only) to rise meters from the original waterline)
- the center of gravity going down, making your GM go up, and making the movements of your ship harsher
- excess space, a lot of space in the area you put these things you have no real use for now
and all implications of that on crew, stability, resistance and battle abilities.
I would suggest setting 2 Mk 26 as secondary launchers and set an Mk 10 or something like that as primary missile system. that way you get SM-1 (and even 2) ER instead of MR as main weapon, which really adds a lot.
ASROC had an dedicated sonar, IIRC that one was both on CFA class and on the spruances. should look that up to be certain though, but I have no time right now, ask me later if you are uncertain