Thanks utnik for the comments. This is not a case were any solution seems "right on target". The 500+ pages are a mix of text and pictures (photos and drawings). OCR, proof-reading and typesetting a new book with pictures would probably be a lot of work (say 4-5 weeks) - and we still end up with just a "copy/facsimle" of the book. "Same, same but different".
Updating the book, an alternative we considered, would not be an option either - it would be better to start an online wiki with local history that could continuously be updated with new research. The current book is "frozen" with the state of findings up to 35 years ago and we would like to avoid that.
So, the current suggestion is to make a "ebook" of the old book scanned today, as simply as possible, and try to get financing to create a new online wiki, using the old book as starting point.
I understand that Scribus usually has other use cases, but for now I'm looking into all options.
Dan