Some warships which survived WWII were given updates during the late 1940s or 1950s, for the most part modest changes to keep them current a while longer. In terms of being the most dramatically altered, a few examples stand out including the two WWII Baltimore class gun cruisers transformed into the US Navy’s first guided missile cruisers; USS Boston (CAG-1) and USS Canberra (CAG-2).
Of all WWII warships later rebuilt, Taiwan’s Wu Chin III modifications to Gearing class destroyers may be the most amazing. Unlike the cruisers above, the Taiwanese were packing more technology into smaller hulls; they did not have the Pentagon’s budget to play with; and most amazingly this was done not just years after WWII ended, but almost a half-century later.
(The Gearing class destroyer USS Power (DD-839) at the end of WWII.)
(The Wu Chin III-rebuilt destroyer ROCS Shen Yang – the former USS Power of WWII – in the 21st century.)