Andrew J. Prewitt also has service records as 2nd. Lieut. A. J. Prewett in the 20th. Regiment Confederate Cavalry (Lay's).
A capsule history of this unit is available here - http://mississippiscv.org/MS_Units/Lays_MS_CAV.htm

There is also a 2nd. Lieut. A. J. Prewett listed as a member of the 24th. Battalion Mississippi Cavalry (Moorman's) in the final surrender roll of this unit. http://mississippiscv.org/MS_Units/24th_Bn_MS_CAV.htm

Service records for this soldier can be ordered from this site -
http://history-sites.com/research/index.html