Right hand "rail" of the Norinco receiver isn't flat, and the stock needs relief on the right hand side to allow it so sit flat. If I were you I would trace the outline of the receiver on the stock, inlet it to sit flat, and bed with epoxy under that surface, the left rail and the heel. If you do a good job, you can't see it, and the receiver will sit like it should, even better if you can elevate the front of the receiver slightly to put the appropriate tension on the stock ferule to barrel band. I have an old post on here showing pictures of when I did it.