Mark, I also had an ancestor with connections to Dibrell's 8TH Cavalry and wondered if you knew that it was also referredto as the 13Th Cavalry as well also was sometimes confused with the 8TH Smith's Cavalry. I also do Civil War Research, and know how things like this can throw off finding information on records. I was also wondering about the amount of information on muster roll records. I have found some with pages of information while others are only a couple of pages, with maybe when a soldier enlisted and nothing else while other have all the information. Here is some links that you may find interesting on the 8TH Tennessee Cavalry Regiment.

http://www.dibrell.org/
http://www.tngenweb.org/civilwar/csacav/csadibrell.html
http://www.tngenweb.org/civilwar/csacav/csa8cav.html