Ending Domain A & Passing content to B

Managing dupe issue

[henry0]

Note: as per a new thread to be in accordance with tedster I do not use the term: Site but: Domain :)

Here is my predicament
I am passing assets from a business A) to one of the new LLC I just created; including my “main” Domain

We wish to keep the new domain mostly like a CC copy of A) domain
But with some additions and very few content existing changes
So the “Old” A) content will be passed to B)
Then I will remove A) domain presence

How can I address this

Two problems
1)cleanly ending A)
2)possible content duplication issue even if A) is no longer reachable

Thanks for any input