The only William Harrison in the 9th in 62 was an
R. William Harrison, Co. A, 9th Texas Cavalry Regiment. I would bet that your Harrison was from higher command in Trans-Mississippi.
I do not have any thing on the 3rd with the 9th. Anything you have on the 3rd getting Horses in Arkansas for the 9th or any one in Whitfield/Ross Texas Cavalry Brigade would be appreciated. By the way are you related to Colonel Jiles S. Boggess, orig Co. B, who commanded the 3rd Texas Cavalry Regiment for a while?