Have you looked over this NARA website? http://www.itd.nps.gov/cwss/soldiers.cfm

If this man served in the army as a volunteer at his advanced age, it would not be unusual in AL, but in Texas he would have been far more likely to have enlisted in the Texas State Troops, if anywhere. From time to time, TST were mustered into C.S. Army service (e.g. coastal defense). All these temporary musters I ever found were for 6 month durations. You might contact the Texas State Archives and see if you can persuade someone to look him up. They will ask for all the info. you have on him, including his county of residence which appears in doubt. Good luck.

Joe