George D. Davis and Wallace P. Davis both served in (new) Co. B (formerly Co. F), 39th (Hawthorn's) Regiment Arkansas Infantry. Wallace's name was mis-transcribed by the compilers of the Compiled Service Records as "Walter".
Also, George D. Davis may well have later served with Hill's 7th Arkansas Cavalry, sometime after the Spring of 1864. Hill's mounted regiment was reinforced with transfers and details from various Arkansas infantry regiments, in preparation for Price's Missouri Campaign in the Fall of 1864. Unfortunately, there are no surviving muster rolls from that period.
The brigade in question was Fagan's Brigade.