I have access to Daily Oklahoman Archives. I found a James Shepard who, in March 1967 was shipping out to basic training in Calif. His father was Dewey Shepard from Edmond. The young Shepard was married. Said wife remained in OKC'

I've found two Dewey Shepards who were alive in 1968.
This on social security death index
Dewey F Shepard born 1934 died 12 24 1997 Enid OK
Dewey Shepard b. 1899 died OKC 1978
Their obits might tell you something. contact library in those cities for obits or how to get one.
Of course, this James Shepard I found may not be yours. mh