I found a 1946 wedding announcement for your grandparents from the Dixon Illinois newspaper that I thought might be of interest to you. The following link (below) should take you there, then scroll down until you find the Dixon newspaper article. If the link does not work, send me a private email with your email address and I will send you a copy of the article.
Also, have you checked with the funeral home who handled Alma Ackman's arrangements or the cemetery where she is buried or her obituary? Either source may tell you where James, Jr. was in 1976.
http://search.ancestry.com/cgi-bin/sse.dll?gl=38&rank=1&...