According to Wikipedia the last three are
HC:50 The Editor's Introduction, The Reader's Guide, and Index
I have not seen any online version of this volume.
HC:51 Lectures on the Harvard Classics
Available thru
http://www.bartleby.com/60/
I am converting this to a RTF right now and will try to make a LRF when done.
HC:52 15 Minutes a Day Reader Guide
See the RTF above.
Mark