Bud's of mine worked down at CMP, collected fully correct rifles, or mostly correct rifles, and sold the parts. They made much more selling parts than the value of the rifle. I did some horse trading, getting correct parts for my late model M1's.
All correct and new Winchesters did get out the door very early on in the CMP days. One work day at CMP, went I put in some free time, one worker down there told me he made sure the orders that went to Alabamians got very valuable rifles. That was still in the one rifle per lifetime era, and I had already got mine before then!. Guys would come out to the range with these excellent condition, like new, HRA's, IHC's, Win 13's, that they had just received. A good friend of mine got a 1941 gas trap conversion, all correct.
That was a long time ago and that period was short and ended as the CMP decided to make as much money from their rifles as possible. Typically what is floating around now are restorations. Guys buy parts and restore the rifle as best as they can. There are always arguments between collectors as what constitutes correct parts. As I recall, during the 1950's Springfield Armory supplied parts to HRA and IHC and rifles with SA barrels by these vendors came out in sufficient quantity to prove they were not rebuilds, stuff like that. There is always an argument about the internal, unmarked parts, as who made them.
Stock stamps have been remade and there are guys who stamp stocks with WW2 SA, Winchester, HRA, IHC stock cartouches.