The easy button option would be a chassis. Since they are solid single shot recievers ....putting them in traditional BDL style 700 SA stocks would require you use a bottom metal or a hinged floorplate with the spring and follower removed. Or having a custom stock fitted or made.
Not sure what you plan to do refurbishing wise or intended usage.
Careful....ARA specifically states 40X's are not factory class rifles. Learned just recently that my 52B is also not applicable. Basically any rimfire rifle with true hardcore target shooting pedigree (even left original) is an Unlimited gun. Dumb....but whatever....I get it. They want a category for the Kmart guns of the world.
You put a no BS benchrest stock on over the factory wood one....perhaps you run afoul of whatever organization rules you are playing under.
Boyd’s might make you one. Just call and tell them you want a 700 inlet stock with no magazine inletting. A couple of the big stock companies make a stock for a 40x. You can also just take any blind magazine stock and fill it with epoxy. I debated buying another stock for my 722 based 40x but I just decided to pillar bed and glass bed an extra factory stock I had.