Thanks to a kind soul, I now have a 3D printed stock on my Winchester 12. It replaces the original wood stock, which is cracked at the wrist like many others.
Since their 3D printer's envelope is only about 8x8x8" it is a 2-piece* model held together by 4x wood screws, which I welded together once assembled.
Its geometry mimics and matches the original in the LOP and cheek weld except for the slightly extended bottom of the pistol grip. The originally fitted Pachmayr buttpad mathches perfectly. Finally, I can shoot this beauty.
*Sorry, I goofed: it is a 3-piece model because the buttpad sits on its own insert into the buttstock.