I looked on rootsweb.com on the social security death index. There is only one listing for an Edward Killackey passing in 2001. Birthdate: 12 dec 1914-Matches! Death date: 14 Feb 2001-Does this sound right?
Last residence was zip code 48654 in Rose City,Ogemaw, MI! I think this is your grandfather.
His SS# was 376-03-1893.
You can write tothe SS adminsitration and get information from his original application to the SSA. This may be a good starting point for you!