Postwar naval guns worth retaining

Which naval weapons discarded after the Second World War would have been worth retaining or reusing?

The answer favors more 40 mm weapons on Fearless and Intrepid, continued use of the 3-inch gun, and development of twin 4.5-inch mounts rather than a shift to single guns.

The answer values weapons according to the later threats they could still address rather than their age. Additional 40 mm mounts would have strengthened amphibious ships in the Falklands, while the 3-inch gun retained useful medium-caliber potential. A twin 4.5-inch mounting costs more to maintain but provides an immediate increase in volume of fire when combat begins.