First question; does it fire, and the safety work? The Germans numbered so many parts for a reason, not just to mess with collectors. Some substitute parts are far enough off in dimension that they won't interchange. If it works, don't sweat it. As for headspace, I think that's an overblown (pun intended) problem, especially on the well-protected 98 action. Unless the headspace is so excessive that you get split or bulged cases, or can't close the bolt on a round, it's not a problem. One quick and dirty way to check headspace is to put 2 layers of masking tape on the base on an unfired round. Work the bolt and eject the round. If the tape is scratched and torn, your headspace is probably OK. If you're really worried, you could buy a set of headspace guages.