For illustrative purposes, the top gun is a Romanian Draco. The bottom, an M92. For a VZ stock it needs the anti rotational top notch and the factory rear trunnion is simply drilled and tapped. It is also a bit thin so an additional nut is added to tighten and hold the screw.
CNC now offers a single bolt/nut rear folder that is the simplest method to attach a stock that I have yet to encounter. NFA applies.