Using Ancestry, I've located your Isaac in Pulaski Co. Indiana in 1860; in Howard County, Ks in 1870 (before the county split into Elk and Chautauqua), in Elk Co. in Longton in 1895, then in Howard City in 1905 and 1910. The 1905 and 1910 listings show just Isaac and Sarah J., the children are all grown and on their own. In 1910, it shows they've been married 44 years, and that Sarah has had 11 children with 9 still living. The 1860 listing shows Isaac as age 33 and in the household with William Benefiel age 63 and Jane Benefiel age 59. Might be his parents. Also in the household are Sarah J. Davis, age 21; Lydia M. Davis, age 16, and three children with the last name of Dunlap: Joseph age 9, Marilla J. age 6, Adaline, age 5; lastly there is an infant Annie M. Davis, age 3 months. Based on ages, Sarah J. Davis may have become Mrs. Isaac Benefiel.
The 1870 and 1895 census listings have several of the children listed. If you want to contact me separately, I'll provide more info on them.
ddurbin1@cox.netKnowing the death dates, some kind person there in Howard might be willing to look for a microfilmed obit at the library.
I'll keep looking for Isaac and Sarah in the 1880 census. They must be there under a different name spelling.