June It is a pleasure, I know you have been doing this research a long time. James and Matilda are my great-great, John T. and Lucy May are my great and Clyde Aaron is my grand. Now I have the connection to Abraham III and that they were first cousins. As far as the marriage date, I have relied on LDS information of abt. 1858. I would like to find more information of the marriage record. Sounds like you have looked in Washington County information with no results.
NW Ark. Gen. Soc. 1980 publication of the Cem. of Wash. Cty, Elm Springs Cem. lists Aaron, Matilda C w of James, same/stone/with James and all the documented dates in mo/day/year of birth and are correct for both people.