George,
Almost all Darnes have a threaded rod in the wrist. It has wood screws on the outside, and machine screw threads on the inside. That same rod makes it almost impossible to bend the stock for the cast, right or left, that you need. I always tell people to forget buying a Darne that doesn't fit.
It looks like a good, but, advanced, gunsmithing project that will keep you out of the pool hall in the coming year. Enjoy it.
The design of your gun, and, a Charlin sliding breech gun, miss the true advantage of Regis Darne's model R and V sliding breech guns, in my opinion. That is because they both feature a pin in a hinge, same as a Purdey or a Stevens, or the hinge on a barn door. The model R and V guns avoid that, and spread the wear surfaces out over the entire length of the gun's action. I've never owned a P, but, have examined quite a few, and wouldn't likely turn a decent one down if it came my way and it fit.
That said, most of us won't live long enough to wear a gun out from using it.
Do keep us posted on your progress.
Best,
Ted
