1) Check the Federal Census for 1850, 1860, 1870 and 1880 to track his location.
2) Didn't find his name pop out in these transcriptions for the Choctaw territory, but don't take my word for it -
The 1860 Federal Census of Indian Territory
3) This Find A Grave has some effort behind it.
Benjamin Carven Heard was born on February 27, 1835, in Fayette, Alabama. His family later settled in Hot Springs County, Arkansas. He moved to Le Flore, Oklahoma in 1860 and became a school teacher. He later served in the Confederate army 1862-1864.
www.findagrave.com
Check the right hand side for Ancestry links - the 1850 and 1880 Federal Census look legit but the TX and AR death certificate repositories are for time windows after his death in 1888.