I am currenlty scratch building a representative late hawken. After studying Hawkens for some time, as far a "authentic" goes I have formed some opinions, probably wrong but here goes. Orignial rifles varied quite a bit. If you want a copy of some particular original, then copy it. That will be difficult to do without out actually taking the original apart. The ability to examine an original close enough to truely copy it is not for most of us.
Modern parts sets rely heavily on castings, casting were not used to that extent on originals. If you get too spun up over some parrticular detail it may bog you down to actually building the thing. For instance, the crook in the toe line of Kit Carson's rifle. To me it makes no sense other than a construction error on the original. Maybe they did the more than not, I have no idea. But if you want a copy of that rifle it needs to be there. But how can you copy sometthing you never touched? Modern locks and hammers are only close. Trigger guards vary. Nose caps are difficult to get right. Wedge locations may not be what you want. It goes on and on. I say just build one that has representatinve features and enjoy it.
