BBM1 (the whole paragraph really): You do a really good job of conjuring up the time and issues. This was a really big theme of TV shows in the 70s and 80s. Do you remember?
BBM2: Love this as a title
Along the lines you and Odyssey are discussing, I wonder, couldn't we also post something in the comments on the NamUs page, where there's already some chatter about people knowing Sylvia from Tottenville High School -- like a classified ad? Maybe something like this:
"
Do you remember Sylvia Lwowski (Tottenville High School class of 1971)? We are a group of caring, amateur sleuths, attempting to put the pieces of Sylvia's story together in order to understand how and why she disappeared in Sept. 1975, and we need your help. What do you remember about who Sylvia was as a person? What was going on in her life when she vanished? Visit our web-based forum (link) and read the ongoing discussion about Sylvia's disappearance. If you decide you'd like to contribute, just register (involves picking a screen name and password) and chime in (participation is free and anonymous)! (Once you register, you also have the option of privately messaging any one of the posters.) Please pass this along to anyone you know who knew Sylvia. Thanks."
Just putting it out there as a starting point ....