I restocked my TC Hawken with a Pecatonica River stock years ago.
It isn't a "drop in" project and there is some work that has to be done to get everything to fit. Much of it is minor trimming that can be done with an Exacto knife (Hobby knife with a pointed razor sharp blade), but as I recall, I also had to remove a little wood at the rear of the barrel channel to remove the radius that was left by the cutter that formed it.
When you use the hobby knife on the lock mortise, place the lock into the cavity as good as you can and keep the blade against the metal edge, using the lock as a guide while you press the pointed blade into the wood. It can take several passes around the lock to get the mortise enlarged so the lock plate can fit down into it. Also, it is a good idea to use some sandpaper to dull up the rear of the blade next to the handle. If you don't you might find your finger has slipped forward onto the blade. You won't know it at the time but soon you will see red spots of blood appearing on the wood.
Here is a link to a topic that is talking about the Pecatonica River stock for the Hawken. I made several posts in it and you might want to read them.
https://www.muzzleloadingforum.com/threads/pecatonica-stock-on-renegade.64102/#post-778253