Odd, I don't see the holes in the stock to screw in the butt pad. Maybe the Kick-Off unit is mounted a clever way?
The situation: A gunsmith has cut something on the order of one inch from the back of the stock to adjust the length of pull for a shorter person. The person now wishes to increase the length of pull back to the original.
1. What's the length of pull now? What is the length of pull desired?
- If only a little was cut off (half an inch or so), the result might be achieved with a thicker butt pad. Easy peasy.
- While fussing with the wood, this may be the time to fit the LOP exactly to the new shooter. Maybe the LOP should be increased greater than the factory original, or the pitch of the stock (angle of the toe) changed?
2. How neat is the original cut? Line up the bit cut off with the stock, show us how nicely it fits!
3. It's possible to make the piece cut off be a removable spacer, so the stock can be either long or short. Since the wife is shorter, it might be nice to have a gun for her should she change her mind or for a youth or small guest.
4. How much does the OP want to pay?
After attaching the cut-off piece, in order to make the stock look like there was never a cut, the whole stock will most likely need to be refinished. If a neat professional line is acceptable, then the job will cost much much less.
My perspective: I am a shorter than average man. A stock that has been cut off professionally on a nice gun like that is WORTH MORE to me since I do not need to pay to have the stock cut off!
It seems a waste to lengthen a gun that's been custom fitted, turning it back to factory.
If this was for a growing youth, and the OP was not concerned about perfect cosmetics, and the gun was worth more to keep than trade towards a new one, then putting the removed piece back on makes sense to me.
What is involved:
a. Sand the joining pieces until they hand-fit perfectly.
b. Temporarily re-attach the old piece and drill pilot holes for hardwood dowels.
c. Reassemble, making sure the dowels are a perfect fit, or stretch holes until they are.
d. Final glue-up, with plenty of clever clamping to get a really strong bond.
e. Cosmetics details on the exterior.
Some might say "You can do a good glue up, THEN use some quality wood screws or dowels to secure the joint from tension or shear stress" and maybe they are not wrong.
In my case, I would want a repair that can be un-done. We know a shotgun for a shorter person in the family is needed. Maybe it will be desired again, in the short version!