Grafting a new back portion to the old stock is a somewhat common way to fix the 'cut too short' butt stock' or one that has alterations and splices added to it to fix dimensions.
The existing stock is cut, usually at an angle just at the rear of the checkering pattern at the grip and to match the checkering line(s) or border.
Then a new piece of wood that matches as closely as possible is attached or grafted to the original front section.
This saves doing all the inletting for the action though some trigger guard tang inlet is usually in the work.
The graft/attachment is sometimes done with a biscuit type joinery and glue. Others use a strong wood screw into the new blank from the orig piece along with a dowel and glue.
Once fitted, the back end piece can be shaped to what ever specs the shooter wants incl new LOP, cast off/on, etc.
The orig checkering pattern is redone and picked up and if the work is carefully done the checkering pattern lines will fall right along the joint which should be so carefully fitted as to be nearly invisible anyway.
Any difference in color or wood streaking can be easily matched betw the two pieces as it falls within the checkering pattern.
A Butt-Transplant for a gun.
I have another one to do now on a SBT Lindner . I think I have a decent piece of wood for the project. Just need the time.