Any buttstock will "fit" any frame, they all mount the same way by a bolt through the wood into a threaded piece at the rear of the frame.
The newest centerfire rifle frames, the ones from "NEF", are stronger than the ones made by the company before their last reorganization. They can be factory fitted with any of several caliber and configuration barrels. Many folks here buy/swap barrels on line and fit them to their existing frames themselves.
Forends on these all attach by a screw that goes into a threaded gizmo welded to the underside of the barrel (an estucheon I think is the correct name of this part). Most forends will go onto most rifle barrels but some of the shotgun barrels, the ones that are rifled, are quite a bit bigger diameter and require a larger channel in the wood. Mostly, any rifle forend will attach to any rifle barrel as long as it is of recent manufacture. (not sure of the date but older, like '70's and before, guns had the forends attached by a spring loaded pawl that grabbed a pillar soldered to the barrel. these older guns are not marked NEF and are no longer available new unless you find one in a collection somewhere.
If you buy a new NEF rifle you will get a listing of available barrels in with the packaging. There is also a listing at NEF's website:
www.hr1871.com