From "Lone Star Regiments in Gray," by Wooster:

"Bradford's regiment was one of the units created late in the war that was not given a numerical designation. Since Bradford left the regiment sometime in early 1865, some accounts refer to the unit as Mann's regiment, so named for Col Walter L. Mann, who commanded the regiment in the last months of the war.
Muster rolls indicate the regiment had only 9 companies, some of which were quite small. Only 243 officers and men were present for duty at Galveston in Sept. 1864, but the number rose to 388 by late December. The regiment remained in Galveston until the war's conclusion; returns for May 10, 1865, list 26 offucers and 369 men present for duty."

Wooster's footnote indicates much of this information came from the Official records.

Sifakis and "The Compendium of The Confederate Armies-Texas":
organized in spring 1864. Surrendered May 26, 1865.
1st Commander: Charles M. Mann
Field Officers: Thomas R. Hoxley [Major]
Walter L. Mann [Lt Col, Col]
John E. Oliver [Majpr]
William f. Upton [Lt Col]

Assignments: Western Sub Dist. [June-Sept 1864]
8th [McCulloch's] Texas Cavalry brigade, 3rd [Drayton's] Texas Cav Division, 3rd Corps, Trans Miss Dept. [Sept 1864-March 1865]
Defenses of Galvestopm [March-May 1865]

Official Records: Jan 30, 1865-[Kirby Smith to Gen Walker}-
....."Gillespie’s, Anderson’s, and Bradford’s regiments sbould be dismounted and made part of the garrison at Galveston.............."

"Texas in the War" Simpson & Wright: Bradford's Texas Cavalry regiment was referred to as "Mann's Regiment" late in the war as W.L. Mann took command of the regiment in the spring of 1865, when it moved in to defend Galveston."
Footnote says: "Fitzhugh states that Man's Texas Cavalry Regiment was the same as Bradford's, but both Henderson and Wright list it separately."