JBoyle wrote:
When discussing warbirds it helps to have a very selectrive memory on this topic.
Many flying Spitfires, Hurricanes and Mustangs are probably closer to being replicas than "real" aircraft. This includes many seen as "national treasures".

No, absolutely not. There are a number of specifics here, and the focus on the prestige fighters is a distraction from the majority of mediums and heavies which are predominantly original.
The second point in the specific is that the Flug Werke machines are not part-exchangeable with genuine Focke Wulf parts. Like kitcar copies of prestige cars versus the rebuilt originals, they provide a fun, 'affordable' alternative to the original, but are
not a machine restored to original standards using parts and techniques that are as the machine was originally manufactured.
There are also people and organisations that closely monitor the restoration business. Certainly there are regular efforts to wander in with a data plate in one end of the workshop and wheel out an original the other end; however as a close observer of this business, I am comfortable that the degree of originality is known (and establishable - if not shouted about) of any major warbird. Specifically I for one am comfortable that the degree of originality of any airworthy Hurricane is known, and documented.
You are quite right that there are Spitfires (and I'm sure Mustangs) flying that started from a lump of corroded metal less than three sq metres in size. However the rebuilt machines - certainly Spitfires and Hurricanes in the UK - while containing new metal and workmanship are reconstructed to the same design standards as they were originally. They do not contain modern substitute equipment, but new-old-stock, or painstakingly re-manufactered parts. Changes are very hard to introduce, however beneficial they may be. The variance from original material - the amount of which as I say is known - is a degree of pedantry that is of interest to specialists and (non-flying) national-level collections. Which is why we also have them.
Just because the majority discussion floats about on the 'looks like a duck' and 'grandfather's axe' level of analysis does not mean that superficiality applies to all.
Regards,
PS - I am using the term 'replica' in the lose, general, rather than the precise museum standard of the concept.