How an undead statblock differ from its living counterpart?
The question has been changed from the original question. However it seems people think it can be improved to be stackable. The current question itself already has an answer in a comment (and possibly another one).
At this current state, the question ask "is there a pair of monsters, that provide statblock for its living and undead counterpart?" which is basically a content identification (if my interpretation is correct). The content is already been proven by another user that it exists, and I don't think it's opinion-based, too broad, or unclear.
What this question needs to be opened?