Thought I'd add these particulars. Although I believe there's a tombstone dating conflict I also found a 1870 US census record from Kansas, Fort Scott, Ward 2, Bourbon KS that shows his name with a birth date of 1845 and from Ireland. My gr-grandfather, father of Williams wife, was a Major in the Civil War and was stationed at Fort Scott where he also homesteaded. William didn't marry my gr-grandmother until 1877. To add to the possible confusion is a Canadian census record showing a William Hanna living in St. Patricks Ward, West Toronto, Ontario, Canada who has a birth date of 1847, however it's difficult to track records from outside of the country. That's one reason why I attempted to look up border crossing records in hope of finding him but it was to no avail. Names coincide but dates do not. Perhaps more Kansas research is necessary to see exactly what drove him to travel from Canada to Kansas but I have a feeling he lived elsewhere before residing in KS.
I appreciate your help and look forward to hearing back from you should you find anything.