Not unusual at all for parts to get recycled. Restocking was common. I couldn't say definitively if the gun is restocked or not without examination. Interesting the way a wooden rib was used instead of a full length stock. May have been a way of dealing with a broken forend.
Now, Wheeler made a variant fusil in the post 1800 period, which looked just like a HBC/NWCo. trade gun, except that it did not use a serpent sideplate. The lock was like a NW gun, as were the trigger, guard and rr pipes. I have seen a few of these; they are a definite pattern. No idea for whom they were made. It would be worth taking a really good look at the barrel proofs - are they standard post-1813 Birmingham marks, or are they Board of Ordnance proofs for privately made arms? The reason I ask is that many of the "trade guns", with circle fox marks and serpents seen in ON have BO marks, and were never fur trade guns. They were made and supplied as militia arms during the 1812 War period, or were supplied to HM Indian allies, treaty guns, etc. I have a "MOXHAM" NW gun (1813-1818) with such marks, along with the brands of the Indian Departmrnt of the British Army. It was my suspicion that these Wheeler variant guns may have been made and supplied during this period.
I am not a fan of reconversion. It destroys much of the historical use of the gun and turns it into a representative specimen at best. A significant amount of welding and refinishing is required. I do not believe that reconversion adds value to an antique, and diminishes its value as an artifact.