Couple questions. When upgrading from UBBT 6.5 are the old post/topic numbers preserved during the import.

Also, is there a redirect script available for some key scripts like showflat/postlist that can redirect to the proper locations in the new board so that historical indexed pages aren't broken?

I don't believe the post or thread id's are preserved (it isn't an upgrade, it's a completely new product, using an existing name), however there are redirect scripts included in the importer.

Looks like an IMPORT_MAP table is made during the process with the old post->new post mapping... and that is how the redirect script works.

That will do!

Yup