Moving an non-WP, non-blog site into WP – how to plan?

I’m helping a pal with an old site with a lot of cruft. I want to pull it into WP — perhaps with the bulk of the old stuff archived. However, there are some legacy pages with some links/traffic.

Example: say it was wayoldstuff.net, not stored in a database, with URLs iike
wayoldstuff.net/cafe wayoldstuff.net/tales, and wayoldstuff.net/tales/picturebooks

How should I approach this? All of that could go into WP archives pages, and let google reindex to figure things out. Or would you create those pages on the new site? If so, would there be a way to create them in WP and keep the old URLs?

Thanks!