Try the following:
Henry Ford Centennial Library (313) 943-2330, 16301 Michigan Avenue, Dearborn, Mi 48126. http://www.dearborn.lib.mi.us/default.htm
Has the Detroit News from 1955 and the Detroit Free Press from 1970. To request a lookup for death notice/obituary, send SASE to above address Attention: Adult Services. They will not respond without the self-addressed stamped envelope. This is their policy as of December 2008.
If they don't have it, I would find out more from the niece. Does she know this from personal knowledge-visited him prior to his death in GP. He could have had his SS check sent to Michigan but actually lived somewhere else and had a family member taking care of expenses. Do you have his date of birth and birth place? Was he married? Have you found him on any censuses? Looking at Ancestry, I didn't really find much for someone with his name here in MI.