OK, now it's my turn for a rant!
I shoot old rifles. Some of them very old. Some of them look like wrecks - on the outside. The insides are a different matter! Many would be sneered at by collectors. But they all work. I invest some time and trouble to achieve this, and share the methods with people on these forums.
If part is defective, I will repair it or (rarely) replace it with an original part. Basically, I will carry out what I regard as proper maintenance (like oiling a dry stock). But not pretty it up to increase it's decorative value. The aim is to keep the gun functioning as a gun, not as antique decoration.
Swapping out properly functioning parts merely to achieve an imagined "correctness" is IMHO falsification. Take a close look at the M1(carbine and Garand) forums to see how the "numbers game" can become obsessive. Thanks to the efforts of the "matchmakers" there must be a higher percentage of "all original and correct" rifles around now than there were when they were in service use, as the matchmakers busy themselves to undo the work of Peter Laidler
and his colleagues around the world.
Force-matching numbers on replaced parts is totally non-functional, and has the character of forgery, as it is the falsification of documentary evidence (the number). There is no excuse for this whatsoever.
I am not a collector. I am not running a museum. I am not saving them for posterity. Posterity is a person I am never going to meet, and will have to look after himself. But posterity will reap the advantage of the work I have done in making and keeping these old bangers operational, instead of just hoarding them.
Collectors who, with misplaced pride, write "I have just acquired my 99th 4T (or whatever)" are not doing anything useful for the shooting community. They are, again IMHO, being dogs in the manger and preventing 98 other people from being able to shoot one of these rifles.
And then they have the temerity to complain that prices are rising - when they themselves are the price drivers!
Sorry collectors, I know this is unfair to some of you who are serious students of the material, and hereby apologize to those who feel unjustly criticized. But all too many appear to be hoarders. And this is merely the opinion of a serious shooter, so you can ignore it!