I don't know if any of this ties in to your family or not but I will post and maybe somewhere down the line it may be useful...
In the Riverside Cemetery located in Seely, (North of Hayward) there is a Sanny Sjostrom Munger 1903-1929
also a Donald Munger 1923-2000 and an Anna Louise 1854-1931.
Also off the cuff... I grew up in Hayward and lived in MPLS for several years. I worked at a cleaners located at Lake&Chicago, this was 1988-1989ish.. An elderly man who's last name was "Munger" used to come in and said he used to go to Hayward on business, think he was in clothing or sales of some sort...I don't remember what his first name was.