Older Model 1100 20 gauge stock and forearm

[Virginian]

What you have is a standard weight 20 gauge 1100. It was made on the 12 gauge sized receiver, and is an excellent gun. Because of the extra weight, a lot of skeet and other target shooters usually hoard these guns. A 12 gauge buttstock will fit fine, but the barrel channel of a 12 gauge fore arm will be too big. You can try to find a used set in good shape - noot too good of odds. You could buy a custom stock set, or you could buy a 12 gauge set and "adapt" a 12 gauge forend by filling in the barrel channel gap with wood or some AcraGlas. I have seen one done with AcraGlas and you would never notice it at first glance.
Another alternative would be to refinish your stock set. It isn't as hard as it sounds, particularly if you use MinWax stain and Polyurethane rather than an oil system, and the mahogany looks great.
You might find something here, too :
http://www.gun-parts.com/remingtonstocks/
Good luck.
P.S. - barrels carry a premium, when you can find one, so you may want to get someone like Mike Orlen to install choke tubes for more versatility.

[Virginian]

That's an 1100 fore arm and an 870 buttstock. You can drill out the hole and put washers behind the action tube nut and "adapt it" if you want to keep it.

[Virginian]

Hey, I'm surprised that second generation style forearm fits. I'd consider that a "win" all by itself. 12 gauge sized buttstocks are plentiful.

[Virginian]

The fore end checkering pattern is 2nd generation, introduced in 1979 (buttstock is a second generation 870 - first generation impressed checkering - which coexisted with the first generation 1100). The standard receivered 20 gauges supposedly stopped production in 1978. "Most" standard 20's came with walnut. I have heard some standard 20's were made after that but have never seen one. Have you put that fore end on the gun and tightened the magazine cap and everything fits snug? That might be a LightWeight 20 stock that someone opened up at the back to fit a 12 sized receiver. All the fore ends should cover the same amount of receiver.