Who would win between the historic battlecruiser Kongō and today's JMSDF Kongō?
Short answerThe modern Kongō would probably win because its missiles, torpedoes, and modern gun systems can disable the older ship quickly.
NotesThe modern JMSDF Kongō has the advantage despite the battlecruiser's 14-inch guns. The older ship can threaten at artillery range, but the destroyer carries eight Harpoon anti-ship missiles and other guided weapons. It also has torpedoes and an OTO Melara 5-inch/54 gun able to fire long-range Vulcano ammunition. Those systems let the modern ship attack accurately before the battlecruiser can exploit its heavy battery. Sensors, guidance, and standoff range matter more here than gun calibre alone.