There's four different round butt walnut stock styles that will fit, but only one optional walnut style of which will be the appropriate correct vintage for your model. And one standard hard rubber style.
So are you interested in the correct stocks? If so, they look like this:
And the there's the correct vintage walnut factory target stocks that will properly adapt the rd butt to sq butt (as DWalt posted about above) with out the gaps that your current stocks have.
They are hard to find and expensive but look very similar to this I frame version: