In January 1961, a six year old named Rose Marie Riddle was kidnapped from a migrant work camp in California.
A pregnant woman lured her into a car, later identified as Dixie Lindsey and the driver was identified as Richard Lindsey.
Richard wanted a young girl for sexual purposes. He forced himself upon her and threw her out of the car thinking she was dead after choking her. Dixie saw she was not dead and beat her with a tire iron.
Dixie fits the physical description as a short, heavyset blonde woman and Richard has a sharp nose and combed back hair. This strongly fits the description of the man and woman who kidnapped Sharon.
The couple had 3 children, and Richard was known to travel around the sound for work, specifically at migrant camps.
The police thought they were strong suspects, but could not conclusively link them to Sharon.
Some more info on that case:
Madera Tribune 17 January 1961 — California Digital Newspaper Collection
People v. Lindsey - 56 Cal.2d 324 - Mon, 07/24/1961 | California Supreme Court Resources