How far along are you on shaping the forestock? Is it still square? I would plane off a few lengths then glue in a layer or 2 or 3 or 4, using the tang as the 'clamp'. Use some plastic wrap or thin tape on the Tang to keep the glue from reacting with the steel and darkening the patch.
I would do one side, let it dry, then the other, rather than both sides in one go.
If not the forestock, then maybe the bottom / toe area, or other off cuts. Using the same wood will help a veneer patch be less noticeable.
Historical? Maybe. Maybe not, as original craftsman never made mistakes