But even if it is just the frame itself, i still wouldnt call it a new P-51. If they are building them for the purpose to make "new" P-51 i still say its a replica.
Personally, I consider a "replica" to be an
exact reproduction of the original. For example, Springfield manufactures a 1911 .45 pistol that is an exact replica of the original GI army pistol the Springfield Armory manufactured in WWII- they make the same gun, from the same factory drawings. These are replicas, yes, but if you tried to look me in the eye and tell me they aren't a "real" GI 1911, because they were manufactured 50 years after the war- despite being identical- I would be forced to punch you in the gizzard. Literally forced; it's an involuntary reflex.
You sound exactly like those guys at gun shows who try to sell me beat-to-shit M1As for twice the price of a new one because they're "all original matching serial numbers." Or those people who insist that the prints of a great ink-drawing artwork are just "trash reproductions" and only the original paper with the ink on it can be called "art," although they all hit the eye and the emotions with the same weight.
Now I'll readily agree that the "intangible" nature of historical value is important. Whether it be as grand as the Flying Bockscar or as chillingly humble as a beat-up Mosin Nagant at a gun show with a stock still stained with the blood of the Russian soldier who died holding it, the fact that you are looking at or touching a remnant of a history that happened is powerful. But by the same token,
a new creation of an old model has an intangible value all it's own. The fact that you can buy a brand-new Springfield GI 1911 makes the gun a part of
living history, not just a remembered one. Recall the awe of the characters in
Jurassic Park when they saw living, breathing dinosaurs again walking the earth- that's the same magic to be found in a new P-51.
I dont think the FAA would approve of the parts being used in original P-51s. They might be precisely the same but the way the FAA regulates things I dont think that would be allowed. Producing "kits" is one thing...
You're right- the German kit frames are designated "AP-51s" (The "Palamino" Mustang) to distinguish them from 1940s originals per FAA regulations. One reason for that (as stated on their site) is to avoid confusion with "original" Mustang parts. Even though they're identical parts, the difference is important to note for the same reason people advertise old rifles having "matching serial numbers-" simply because many people
do care about the "originality" for whatever reason.
The reason that matters to the FAA, I suspect, is one of simple safety- in a complex vehicle that's going to be put under physical strain while carrying a person in it, it's important to know the age of the materials constituting the airframe. If your right main spar was manufactured in 1945- in an era where metallurgy and quality control thereof were less advanced- and it's been put through 50 years of strain and stress in flight, and your left main spar is brand-spanking-new- well, you need to be aware of that. Unknowingly putting together a "Frankenstien" plane can be dangerous.