I have attempted to research the parentage of this David O'Neal as well, but have not found any proof.

I'd agree that the William O'Neal/Elizabeth Stevens from Johnston Co, NC are not viable candidates to be David's parents.

My best guess so far is that David possibly is a son of a John H O'Neal, who appears in the records of both Grayson County, VA and Orange County, NC.

Email if interested in this theory.