As a person who has restocked almost 400 of these guns don’t be mislead by a “ 90%”
In letter stock. Still 100%!of the technical work remains. And yes a 12,16 or 20 gauge are interchangeable if both are of the same frame size, such as featherweights or regular frames ( note: no regular frame 20 gauge guns exist to my knowledge) With that being said, transferring a stock rarely works. Way too much hand fitting initially. Just my opinion here. Jerry