34th - companies recruited from City of Montgomery and the counties of Coosa, Russell, and Tallapoosa.

49th / Co. B- DeKalb

4th (Russell’s) Cav./ Co. B – from Cherokee County, formerly Co. D of the 15th Tenn. Cavalry Battalion.

51st Ala. Cav/ Co. C - Talladega County

51st Ala. Cav./ Co. D – Calhoun County

So, by process of elimination, it looks like the 49th is the one.

After composing the above answer, I have found that William Lackey of the 49th is this person:

Lackey, William, Private, 49th Ala. Inf., Co. B. Born about 1823 in Tennessee, the older brother of Private James Russell Lackey [what unit?]. He married Edy Cathey in 1838 in Benton County, Alabama and Sarah Bryant in 1846 in Benton County, Alabama.

This bit of information is found at http://www.rootsweb.com/~aldekalb/ and there is a note there from a Jim Lackey that I think you will find interesting!