In doing more research, it looks like my father's plane number was not 20 but 32. The full info I have is "42-52690 825 32". The name of the plane was the Rum Hound. That I know I have right because I have an artist's drawing of the nose art. Sorry. This is why we'd love to find someone with information; there seems to be a lot of confusion in what we have.
It looks lke you have the right serial number and nose number for Rumhound. Your dad flew #20, Guardian Angel, on June 13, 1944. Look in the Torretta Flyer index for: Guardian Angel, Bossick, Dunn, Aircraft #20, Mission to Munich. The mision to Munich summary has a list that shows the pilots and planes they flew that day. Mr. Chern flew #20 that day. The letter to the editor from Mr. Dunn's son has an e-mail address that might still be good. Perhaps he has some more info about the crew and aircraft they flew.