There were 2 William Blankenships in Diamond's 10th. One enlisted 9/14/62 in Prestonsburg, Co. A, went through a desertion, capture, oath and rejoining, finally surrendering at Mount Sterling on 4/30/65. No residence is listed. The second William Blankenship, a Pike Co., Ky resident, joined Co. H on 5/15/63 in Buchanan County, Va. and went AWOL on 7/23/63. He had previously belonged to John B. Floyd's Virginia State Line. For further info on this regiment, see Wells and Prichard, 10th Kentucky Cavalry, CSA, May's-Trimble's-Diamond's Yankee Chasers, available in reprint from www.mayhouse.org.
Hope this helps or at least gives a starting point.
Randall Osborne