Doc McGowen/McGowan

I am looking for information on Doc McGowen or McGowan living In Texas around 1870-75.
He supposedly owned a ranch and was a guardian for my G-G-grandfather.Vague I know but if you have any information please let me know.Looking for location to find marriage records for my g-g-grandparents.

Ruble Fielden Simmons b. 1865 (?) p.Texas (?)
Annie Howardb. 1867 (?) p. Tenn

They were married Sept 7, 1886 p. (?)

Thanks for the help!