The S-stacks were standard equipment for all B-25/PBJ since mid production of variants C/D. They were not meant to be used in night missions only.Note the exhaust flare suppressors for night missions.
Those B-25 variants were still in service at Cherry Point and throughout the Navy in Composite Squadrons through the '70s! Simple systems; easy to maintain!
The earlier interim development of the so called "finger stacks" (discussed several times in this forum, modelling section as well) have been developed for night missions in the MTO but also used elsewhere.
Cheers!

