Hi,
Navigate to ~/Documents/iChats and then to a specific chat in a dated folder.
Double clicking it will open in in Messages in it's own window.
In Messages beta (during the last part of Lion as the only/Current OS) the app did read both the new and the old places for storing iChats and the newer saved chats.
Mountain Lion and Messages 7 did not do so good a job.
In Messages 8 in Mavericks the storage position as been moved again.
The current position is in ~/Library/Preferences/com.apple.iChat/Data/Library/Messages/Archive
This contains dated folders for Saved chats like the iChats folder became in later iChat versions.
I have tried adding an Alias to the original iChats folder but this does not seem to work.
I would try making a copy (Duplicate) or the iChats Folder and then try moving the contents to the Archive folder.

8:50 pm Sunday; June 15, 2014
iMac 2.5Ghz i5 2011 (Mavericks 10.9)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad