I am an Angel Guardian Alumni, we do have a Message Board for A.G.O. Formers. You can post a message for anyone who may remember your Dad. There are a few people on Board from that era.
Also, we have had a few Reunions over the last few years for Formers and/or family's of Formers. Although there may not be that many people posting on the Message Board, a lot do attend the Reunions from different era's. We have a list of people who have attended these Reunions.
Our Message Board Site is: www.members.boardhost.com/AGO
Another Alumni's site which belongs to Donna Hunt is called the Fallen Angel Pages:http://www.fallenangelpages.com/home.html
Both of these sites link to each other and also have links to other Formers Websites.
You can also get information by contacting the Archdiocese of Chicago @ http://www.archdiocese-chgo.org/index.shtm
Archive contact is Julie at (312) 831-0711 x 724 or email: email@example.com
Let them know that you want any and all information, ie. Student Records, Sacramental Records, etc. You will need to know the exact spelling of their names, years attended, Name of School, Order of Nuns, which is Poor Handmaids of Jesus Christ (PHJC) etc.
Hope this helps you, if I can be of any help, you can contact me.