This is possible although B-18B aircraft did not operate in the Pacific Theater, expect perhaps from time-to-time from Panama.
You need to create the following devices:
Create the SCR.517 ASW surface search radar by copying slot 1856 ASB to a nearby empty slot. Change Availability to 4201.
Change range from 45 kyds to 32 kyds against submarines.
Create the Mk.XVII depth bomb device by copying slot 203 500lb GP bomb to an empty slot. Change accuracy to 40, reflecting high-drag design
which enabled more accurate delivery on target.
Create the Mark 24 FIDO acoustic torpedo, copy 095 22in Mk 13 Torpedo to an empty slot. Change Name to Mk.24 FIDO, Upgrade to itself, availability
4303, Accuracy 27 (55 actual hits for 204 shots against subs), Dud rate 5.
(After 1943 FIDO could be carried by any Allied aircraft that could carry other air-launched torpedoes such as the TBF/TBM Avenger. About 4000 highly classified FIDO were produced, protected by the code-name Mark 24 Mine.)
Create the B-18B aircraft by copying slot 282 B-18A to an empty slot, such as slot 280. Rename B-18B. Change Type to Patrol. Change Month to 2, year to 42.
Change Wpn 4 from 500lb GP bomb to your Mk XVII created above, Num 4 , 11-Internal facing, filter 64.
Add Wpn 5 as your Mk 24 FIDO created above, Num 2, 11-Internal facing, filter 64.
Add Wpn 6, SCR.517, Num 01, 00-Front facing, filter 64.