Remove buttplate. Use a socket extension and rachet to unscrew the stock bolt (it's in that hole in the center of the butt)
hire it done.
there is the Stevens side by side shotgun model 311
Try e-gunparts.com, Shotgun News, Gun List, do a web search on "shotgun stocks".
The Stevens 311 is a double barrel shotgun.
Try e-gunparts.com
100-300 USD
Numrich Arms has parts for the 311
You may be able to find the information you are looking for through this web site: http://www.huntingsociety.org/gunstocks.html
100-300 USD
I think it is the same as a Stevens 311, made by Savage Arms, for marketing by Sears. A great, utility shotgun. If so, a stock for a Stevens 311 should fit it, but there are two types: one with a straight edge where the stock neck meets the receiver, and the other with a notched edge. Good luck.
$250-$350.
Yellow pages category = GUNSMITHS.