In the written history, most of the ships were in sunk by B25 bombers with heavy nose guns and skip bombing.
Depends on the "written history" you read. Much of the early "history" was written under the auspices of the General Douglas MacArthur Public Relations Unit and so is heavily US centric. The truth is that there was a unified command and the notion of "skip-bombing" was introduced by a RAAF (Australian) high ranking officer who had experience flying Beaufighters with the RAF in the North Sea against the Germans. Remember that Australia, NZ, Canada, etc, had been in the war supporting the Brits since 1939. The Germans had invented the skip-bombing technique. The B-25's did not have 76mm cannons, a claim that you have now edited out. They did have multiple machine guns inspired by the magnificent RAAF (Australian made) Beaufighters. The USAAF B-25's were also crewed by a mix of US and Australian crews. Many only had a US pilot. The AAF were aircraft rich but crew poor, while the RAAF were crew rich but aircraft poor. Likewise the Douglas A-20's are in RAAF markings. The Battle of the Bismark Sea was basically an Australian run operation, a notion that seemly offends US jingoists.
Note that the subsequent strafing of Japanese survivors in the water by the RAAF after the battle could/should have been classed as a war crime. Such was the fanatical bravery of the Japanese forces that they were considered a danger even floating around on makeshift rafts on the Bismark Sea fifty miles from land.
See this for a more balanced view: