First, many postwar guns wearing oversize Target stocks did not ship with these stocks originally; they were added by a former owner.
I'm thinking specifically of the model 66 which seems to have target grips on most (not all... I know a number of 66 owners prize the original standard grips) pieces. Is the number on the yoke of a 66 the S/N?
Not relevant to this discussion, but I'm mystified by a gun maker would stamp "assembly" numbers into parts that appear directly adjacent to the key S/N