Which boyds stock are you wanting to put on the rifle? They do vary on what you have to get or do to them depending on which one. The bottom metal in the picture looks like the metal that I put on my Pro Varmint. Even has the same release lever for the mag.

I've seen photos of the older 11/111 (not sure how old though) where he took out the bottom metal from the synthetic and transferred it to his Pro varmint. The mag housing is the key, if its molded in then no joy, but if you can pull it out, you may be able to swap it straight over.