Tom, basically the same information George provided, but here is what I have on the Spain men of Co A. Not much given in the CSRs as you can see. Really only three muster rolls exist for this regiment, one covering Oct-Dec 1862, another covering Jan-Feb 1863, and the last covering Jan-Feb 1864. I have a note in a file of mine that Richard Spain was KIA in Arkansas, time unknown. I haven't been able to confirm this though.

Spain, Henderson – Private
Enlisted 18 December 1863 in Washington Co, AR by Captain Lea; Present for 1864 muster; No further record

Spain, Richard – Private
Enlisted 20 September 1862 in Dade Co, MO by Lieutenant Wills; Present for 1862 muster; Present for 1863 muster; Present for 1864 muster; No further record

Spain, Robert – Private
Enlisted 29 June 1863 in Cedar Co, MO by Colonel Livingston; Present for 1864 muster; No further record

Spain, William D. – Private
Enlisted 13 December 1863 in Washington Co, AR by Captain Lea; Present for 1864 muster; No further record