Boyd's stock is sized to fit on a 12ga. That means the inletting will be too tall for a 20ga. There will need to be a lot of work to fit it. It will be oversized for the action, so once it is sized it will need refinished.
Once upon a time Boyd's sold stocks for lots of models. I have gotten stocks from them in the past and they had good stuff. One of my 12ga Ithaca 37s is stocked with a Boyd's laminate stock.
However, since they changed/were bought out, they do not offer nearly what they did. A lot of their former employees work at Macon Gun Stocks now.
Jaughtman,
I used a good grade of waterproof wood glue and clamped it back together. I have fixed a couple or mine with cracks there and have a 1951 stock I am fixing that is otherwise pretty pristine for one of my guns.
You can also use epoxy. Gently spread the crack apart and put just enough glue in so that a little will squeeze back out. Just a little. Make sure you get enough inside. You don't want so much that it won't squeeze shut all the way.
Then clamp it and leave alone until dry. Wipe the excess off of course.
If you want to do a stock refinish after the repair, just shout and I will tell you how.
this is that split buttstock above. I glued some walnut to the bottom of the pistol grip and reshaped it back to a more late 1940's, early 1950's profile.
you can barely see the line where the crack was and after I applied the wood stain to match the corncob forend (Ithaca stocks are stained) that line disappeared.
I have to strip the lacquer and respray it as I was trying to get it done to hunt with and you can't shoot lacquer correctly when it is cold. I don't shoot lacquer in the house. You can see on the pistol grip where I ran it, tried to sand it out, broke through the finish a little and sprayed back over. This is minor. A little orange stripper and I will redo it when it gets warm.
Speaking of orange stripper. I mixed some up with baby powder and packed into the end of an Ithaca stock (with some tape around the edges) to suck the oil out of the wood. Ithacas tend to get oil soaked. Usually I just soak them in acetone, but the one I am working on needs to keep the original finish.