Sorry to be a party-pooper about the stock, but I feel there is some misapprehension about the word "original".

The stock on the rifle is numbered to the rifle.
The rifle was made very late in the war.
So it looks to me like the original stock - i.e. the factory used what they had left over at a time when "normal" parts supply must have been breaking down, not what the specification said.
In which case, replacing the (actual) original stock with another to "make it historically accurate" would actually be a historical falsification.

"Original" is how it was actually made, not how it ought to have been. In fact, from the collecting viewpoint, if it was originally made with that stock, then that makes it rarer than an example that is "all correct per specification"!

But that's just my opinion, FWIW.

PAtrick