Hi Reuven,
Look at #7 on this doc. This could help.
https://openacs.org/doc/misc/openacs-pg-migration.txt
Some old discussion about this in here
https://openacs.org/forums/message-view?message_id=31016
OT: How can one use the old bboards on the old site? I would like search on those as the new site uses OpenFTS and it still not as good as the old site.