I want to mount an A2 stock and pistol grip on a old Rem 1100 I have sitting around. Maybe add a railed forend too. Can someone point me in the right direction as to an adapter that would allow this?

Generally you cannot change out the stock on an 1100 because of the action spring and link that run down the tube.  That being said, a company called Elite Tactical Advantage makes a kit that relocates the action springs inside of the receiver.  It is called the devastator.  

http://www.elitetacticaladvantage.com/products/shotguns/devastator/devastator.html

The same company makes a rail system for it as well.  Just keep in mind all that stuff on your 1100 will make it weight more.

looks like they put it around the magtube like the sidewinder by sage industries...i am very interested in that..