It's not possible to get Usenet from the 90s, as it simply isn't archived. 80s is archived via Internet Archive and you can get 10 years worth from 2003 via Usenet king GigaNews.
Google Groups has the 90s, but it's locked behind a 'Googlewall'.
> Google Groups has the 90s, but it's locked behind a 'Googlewall'.
And I believe that is a crime against humanity.
Don't know if I'm being silly here, but is it worth just asking them for it? I'm sure there is some sentimental types in Google that would be cool with what you're doing.