The Adjutant General's reply was to a Duke P. Goodwin who apparently listed his unit as Company K, 8th Texas Infantry.

They found no such Duke, but a D. P. Goodwin, Company K, 12th Texas Infantry, aka, the 8th Texas Infantry.

Based on that exchange, I would tend to believe that Duke Goodwin was indeed, the D. P. Goodwin of the 12th/8th Texas.

Checking the Oklahoma pension records should resolve this, unless you are sure he did not settle in that state post war.

There is one other D. P. Goodwin in Texas units, see below:

D. P. Goodwin, Company C, 15th Texas Infantry (Formerly 1st (Speight's) Battalion Texas, Infantry, recorded on the March, 1865 Regimental Return as furloughed for 50 days, no other records

Based on the fact that he was not recorded on the last surviving company muster roll for the period Jan. & Feb., 1864, it would appear that this Goodwin enlisted late in the war sometime after February, 1864.

This could be the same fellow from the 8th/12th.

M323: Compiled Service Records of Confederate Soldiers Who Served in Organizations from the State of Texas