While shells for the 16"/50 Mark 7 gun could be made - 2700 lbs. for AP, 1900 lbs. for HC - the ~24 mile range just would not justify the effort. Ignoring multiple realities, if USS New Jersey or Missouri got itself all the way on the beach at Guangzhou or Shanghai, only a very small part of the industrial areas would be in range of the 16" guns, and even less area in range of the 5"/38s. Industrial cities like Hengyang or Wuhan are hundreds of miles from China's coast.
One of the weird lessons the USN learned in WW2 was that volume of fire was often more effective than a smaller number of heavy shells. For </= 14 mile range and unprotected targets, 12 or 15 6"/47 light cruiser guns firing 8 or 10 times a minute each, could do more damage than 9 16" guns firing twice a minute.