After you read the W.T. Block history of Spaight's unit, please consider this possibility: Likens formed a cavalry regiment and many men preferred service on horseback so your ancestor may have joined with James B. Likens' 35th Texas Cavalry. Unfortunately no muster rolls have been encountered at the Texas State Archives or National Archives for Likens' 35th Texas Cavalry.
Maybe he served as a witness on a Texas CSA pension application, so you may want to look for men or their widows who lived near your ancestor and applied for pensions.