Looking for some advise on what C6 to buy

[Rruuff Day]

But would that cover that particular flaw (or issue)?

Give Dave or Nigel at RaceReady Garage a call. Mention CCF sent you. They are one of the best Corvette garages in Canada. Tell them what you are considering and whether it can be determined if the heads have been done on an LS7. Here's their number. (226) 887-7103