Dr. Druse compiled his 1968 Blackmore's of Ireland based on his own research and some research he had collected from others.Unfortunately, he did not give clues to the sources he used.I suspect his notes will have been donated to a genealogy society or LDS family history center in Illinois.
My understanding is that much of his later work was simply supplied to him by others, such as myself.You'll note in the Preface that Dr. Druse thanks three people for their work on family's W, X and Y. So, his source for family X was a Marguerite Blackmore, and she gave him this information sometime between 1968 and 2000.Do you happen to know of Marguerite?
So you've traced your Blackmore line back to John Blackmore born in 1846 in Kilkenny, Ireland.According to Marguerite's information John was the eldest and his father's name was also John (X-1).Marguerite and Dr. Druse then deduced that John (X-1) is the same John (C-67) from Dr. Druse's family 'C'.
The '2000' book is an addendum, so it is just the additional information gathered since 1968.My suggestion is to print family 'C' from the 1968 book, and family 'C' and 'X' from the 2000 book, then take the first book and add the information from the second.You'll note in the original that John (C-67) was married twice, but the children were unknown in 1968.The second book just identifies that John appears to match the John in X-1, Marguerite appears to have listed the children but not identified their mother.