Three thought experiments:
1) A company makes Spitfires to the original blueprints, with a few materials changes to sidestep the corrosion problems and a minimal number of other safety-related changes to the original design.
2) In a parallel universe, the war ends in 1942 and 15,000 redundant Spitfire pilots return to a prosperous peacetime. Jets aren't developed, so the RAF holds on to its piston fighters. Supermarine decides to tweak the design to make it more economic and practical for nostalgic private pilots, and to avoid completely disbanding the workforce.
3) Supermarine carries on making Spitfires into 1948, though most never see conflict and are of a type that never flew in WWII.
Would any of these aircraft be real Spitfires?