Shipbucket

Island are also useful for housing admiral facilities.

Agree! The 5"/54 Mk.16 was designed as a twin gun mount for the "Montana" class BBs, but was also fitted in single mounts for the "Midway" class CVB ships (three), so the guns were available at the time, well before the later 5"/54 Mk.42 automatic mount was developed (early-50s, first used on "Forest Sherman" class DDs). They were retained in single mounts for decades onboard Midway, Coral Sea, and Franklin D. Roosevelt, and when surplus mounts became available as the number of these guns was cut from six to three on the carriers, mounts were sold to Japan for their first indigenous-designed destroyer (three per ship, one fore, two aft).

The slender number of US Navy ship remaining in active service prior to mid-1950, many were getting the 3"/50 twin, few could accommodate the newly-developed 3"/70cal.....look at the rebuild necessary for the "Gearing"-class DD USS CARPENTER, as an example.

Given a new CV was building, until SecDef Louis Johnson, former head of Convair (San Diego, CA) - recently promoted the Secretary of Defense -
rules in favor of the B-36 bomber for the future of U.S. nuclear attack efforts, the Navy would certainly have pushed the 3"/70s onto CVA-58, up to the point of cancellation.