I upgraded my 12FV .223 with a new Shilen barrel, NSS lug and barrel nut and put it all in a Bell and Carlson Medalist stock. I also added a single shot feed ramp from SSS for ease of loading. I used the follower from the blind mag to support the new ramp.

My primary advice would be for you to build the rifle that you want. If you can't find the target action, go halfway and convert your 12FV to the 22-250 that you want. If the itch for a target action never goes away, you can still get one some day and build that 22-250 rifle from the components that you already own.