The Camden Benjamin was living in Bethlehem in 1870, but was in Camden by 1880. Where the other Benjamin was in 1880 and 1870 I don't know.
I suggest getting the 1906 obituary for the Bethlehem Benjamin. The Easton Area Public Library and the Bethlehem Public Library should be able to help you find it.
This same Benjamin also received a Civil War pension. He served in E Company 20th Iowa Vol and D Company, 67th Inf: 1885 Appl 549,949 Cert 526,607 Widow Rebecca 1906 Appl 849,332. It looks like Rebecca may have died before her application was approved. Rebecca would have had to prove she was married to Benjamin.
You can get a copy of his pension from the National Archives in Washington, DC for $75. While a bit pricey and the genealogical data it contains is uncertain, it may have some of what you are looking for. As I understand all the pensions will eventually be online, but I don't know the timeline. Some are already available online at Footnote.com for a fee.