Bret:
Using Simpson's Compendium of the Texas Brigade, I am sure that the John Short in I/5 TEX is not yoru man, although the dates of birth would be close. Accordingly to Col. Simpson, John Short was recruited at age 19 on 25 Mar 62 at Independence, Washington County, Texaswas wounded at 2nd Manassas 30 Aug 62, and was killed at Chickamauga 20 Sep 63.
There was a William H. Short in this same company. Could these men be collaterly related to you?
I have some newspapter casualty lists for the retiments in the Texas Brigade, and intend to post them as time permits. My relatives were members of the Hampton Legion, and for about five months in 1862, they were actually in the Texas Brigade, and were permitted membership in the Texas Brigade Survivors' Association; they were brigaded together in Hampton's Brigade on the Occoquan and on the Peninsula in 1861 and 1862, and were in the same division with the Texans off and on through 1863 and into early 1864, when the Legion was redesignated as munted infantry. But they fouhgt side by side with the Texas Brigade north of the James in September and October of 1864. So there was a close bond. But that gets away from your query.
Good luck!