Good luck with the move. It's a big one, but you are correct in realising that it is important to keep the existing posts and data, and that the world moves on.
Short of creating a web service front end to vBulletin and writing a custom Amiga application to access data and present it externally to a web browser, I can't think of a way to get a non-CSS supporting browser to work nicely. And if you create such a web service, you might as well create a non-CSS version of the site, it's such a large project.
