Frommy understanding are the shotgun stocks differ greatly from the ar stocks even though they look the same. The shotgun stock is going to have to withstand higher forces and must be designed accordingly. Now I have the blackhawk adjustable stock and they said the parts weren't interchangeable on the site. Email the company, they can tell you for sure.
Remington 870 12 Ga. Supermag
Springfield XDS .45acp