The first thing to do is to find out if it is the locking bar or the hook and pin that is causing it to be off face. Quite often
it is the sliding locking bar and not the pin or hook.
Hold the action tight against the water table with your hands and see if the gun bbl has movement in and out, if so it is the pin and hook. If not the locking bar and lug on the bbl is worn.
I have just put an old Birmingham gun back on face by TIG welding the lug and filing it down to the proper height to fit the sliding locking bar.
If it is the hook , you can cut a piece of LONE STAR beer can and
adhere it in.