Let's suppose I make a post on a WP site, and a day or so later I see that Google has indexed the page.

About a week later I decide to substantially rewrite the post. Let's say I had to improve the readability with shorter sentences, eliminate passive voice, and tweak the kw's a bit. Stuff like that.



What's the best practices as to what to do with regard to Google? (because the previous version is already indexed)

Should I just simply update the existing post with the new text and leave it at that?
(and Googlebot will recraw the new version)

Or should I delete the old post and make a whole new post with the updated content and a new WP postnumber?
(if so, should I make the title of the new post slightly different?)