Federal prisoner-of-war records are as complete a collection as we can expect from that period. Deaths and burial sites are recorded in far greater detail than found in Confederate documents.

Venus Point on the Savannah River was used for release of Confederate prisoners in November 1864. Any prisoners who died on the passage south from Point Lookout MD would have been buried at sea. I would have to believe that Confederates who died after being released would have been buried inside Confederate lines, which would rule out Fort Pulaski.