I just finished reading through the thread, and have a few random thoughts...
I'm passingly familiar with the murders of Sharon Malone and Cheryl Packard, mentioned in one of the posted articles in reference to Mary Ellen's murder. I had read about their case while researching the February 1966 murder of Debbie Fijan. As I recall, 27 year old (at the time) Robert Kramer--who had already been convicted of previous assaults in the area--was tried and convicted of their murder and thought to be involved in other stabbing murders in the area in the same time frame.
Robert Kramer is kinda (and uncomfortably) similar to Robert Crane, mentioned in previous posts as allegedly claiming to have inside knowledge of Mary Ellen's murder.
And while on the subject of Debbie Fijan, its hard not to mention Richard Otto Macek, whom we discussed in depth on Debbie's thread. Macek, though a resident of the Chicago, IL area, is known to have committed at least four murders in WI (one, at a hotel in Lake Geneva---some 30 or 40 miles from Kenosha). Macek was incarcerated in late '67, released in '71, and committed his first confirmed murder in '72. Some of us who have been researching the Debbie Fijan murder feel that he most likely starting killing after the death of his father in early '66.
Debbie was murdered almost one year to the day before Mary Ellen disappeared.
It's been mentioned in this thread that Mary Ellen had cuts on her face---Macek's signatures, if you will, were biting his victims and cutting the faces (specifically, around the eyes).
On another note, I personally feel that her being found in a hearse was incidental to her murder. The vehicle, a 1948 Packard, would have presented itself as a convenient location to hide Mary Ellen's body (or to commit the actual murder). These vehicles, converted to hearses by the Henney Auto Co, had cavernous interiors. Known as 3-way Side Service hearses, they had large doors on both sides (behind the driver and passenger doors) allowing the caskets to be placed inside from the sides as well as the back. This particular Packard had been painted white with blue lettering advertising a local tavern, and didn't present the typical ominous presence that we associate with a hearse.