Where can I find details on the original manuscripts for the Miyamoto Musashi texts?

Question

I'm doing a "reliability of the text" study and want to review the reliability of the texts that have been used to substantiate the Miyamoto Musashi texts The Book of the Five Rings and The Path of Aloneness. I've already been through all of the websites on the internet (alright, not all of them), and whilst I've found lots of "facts" about the books and the like, I can't find a single scholarly article or reference to archaeology supporting his existence or that justifies that he actually wrote what we have in our hands today.

In particular, things I'm looking for are:

• Datings for the manuscripts
• Number of concordant manuscripts
• Considerations of differences between the published popular works and the originals.

I've been unable to find anything and would appreciate some help.

Answer 1

William Scott Wilson writes in the introduction to his translation (Shambhala Publications, 2002; p. xii),

Musashi's original manuscript of five scrolls no longer exists, but the various copies made differ only slightly in some of the words and phrases. Remarkably, the copy presented by Musashi's disciple Terao Nobumasa to Yamamoto Gensuke, in 1667 (only twenty years after Musashi's death), is still in the possession of the Hosokawa family, whose ancestor, the daimyo Hosokawa Tadatoshi, was Musashi's primary benefactor. It is considered the most accurate of those extant, and it is the copy upon which this translation is based.

For his master thesis at the University of Massachusetts Amherst, Paul De Benson wrote a new translation because "no extant [English] translation is suitable for scholarly reference":

The source text for these problematic English translations is invariably the Hosokawa family manuscript, a wholly unsuitable manuscript for translation.
In recent years, the Harima Musashi Kenkyūkai, a Japan-based research group, has done much worthwhile scholarship on the Gorinsho and has compiled a new annotated edition of the text based on a thorough examination of all extant manuscripts. My translation is based on their authoritative edition and it benefits greatly from their research.

Quoted from the abstract to Benson's master thesis The Gorinsho: Miyamoto Musashi's Five Elements of War.

So you need to access the Harima Musashi Kenkyūkai edition (in Japanese) or Benson' thesis.