New bolt head with ejector/extractor as they come without them usually, new bolt baffle...or a new bolt for about $100 complete,
new magazine & follower as the .223 box has a metal bracket in it to shorten it up. Barrel of course, go gauge, barrel wrench.
Everything can be found at MidwayUsa also.
Being a M12 short action it will/may be a single shot in the .220 swift.