After WWII the US Navy modernized war-built vessels to various degrees for many reasons. Many options were available: new weapons, new radars and sonars, enlarged superstructures, new radios, adding or removing aircraft capability, replacement engines, layout changes, and so on.
Normally one thing that couldn’t be changed was the physical size of the hull. Things could be added, moved, replaced, altered, or rebuilt inside or atop the hull; but at the end of the day the WWII hull was what it was.
In the examples below, extremely dramatic “surgery” actually changed the length and size of the entire ship.
(Not a case of seeing double: the bow and stern sections of USS Navasota (AO-106) pointed in opposite directions during the WWII warship’s 1960s “jumboization”.)
(The WWII submarine tender USS Proteus (AS-19) cut completely in half during 1959. This “jumboization” was one of the most complex engineering jobs ever done prior to the computer age.)