These instructions come to your courtesy of Sylvan Korvus. Thank you, Sylvan!

 
   

Installing Ancestral Recall using the OS X version of LOD

 
 

Step 1

  Backup your AR "Diablo II Patch" file.
       
 

Step 2

  Install D2 Carbon as per Blizzard's instructions
       
 

Step 3

  Backup the file "Diablo II Patch (Carbon)"
       
 

Step 4

  Rename your AR patch file to "Diablo II Patch (Carbon)
       
 

Step 5

  Place the renamed AR patch file in the Diablo II Files folder.
       
      Note: it APPEARS that D2 Carbon ignores "Diablo II Patch". However, for safety's sake, use 2 copies of the AR file, one named as each. This also allows you to play the OS 9 version of D2 in the same folder.