I make a hobby of repairing old doubles to shooting condition. Many have stocks busted in the lock area.
This LC Smith had a chunk the size of an ice cube broken out from tumblers forward. It took many sessions over a week's time to reconstruct it. I inserted 5 dowl pins - 2, then 2, then one more - bonded by Acraglas to bond the broken out chunk to the stock. Then I routed out old wood putty that had been used as an old repair and filled with Acraglas. That was done one pocket at a time. The trigger plate, side locks and action were each fitted separately - bedding with Acraglas where needed. Then everything was assembled and adjustments made to get everything to fit as a unit.
If you blow up the area above the hammer screw you can see a zigzag of the crack. I didn't do any refinish work on the stock. It's an old gun and looks good (to me) as it is.
The problem with these old stocks is they are soaked with old finish and oils. Unless you can get down to dry wood, I don't know what will bond to it.