Lawrence, Great Job and thank you for the information regarding the AGS.
I will add that the ss death index says he was getting his benefits in Texarkana, Bowie county but his death did not occur in that county. I checked the Bowie County Genweb which has county deaths and his is not listed.http://www.hiddenancestors.com/Bowietx/index.html
scroll down and select Bowie County Archives bottom right hand corner, open, then select vital records, open, select Deaths and each year beginning with 1964 is indexed through 1984. Or go direct to this link and select 1973 http://files.usgwarchives.net/tx/bowie/vitals/deaths/