We are moving a site that was built directly in html to a new wordpress cms. Since the site depends largely on google searches it's fundamental not to lose the previous links. But here's the kicker:
1) All old URLs were built in a random manner, he simply uploaded a new file to the server everytime he wanted to create a new page ("somedirectory/page_about_something-4.html") and they will be recreated in wordpress using completelly new urls ("thenewcategory/page-title/"). So it will be impossible to have simply one regex line in htacess, I'll probably need to have a case per case redirect
2) there are more than 6 thousand pages that need redirection. I can't imagine what sort of impact on performance having a .htaccess file would have.
So what are my options here? I'm imagining I could simply keep the old files on the server and make each one of them as a individual http redirect, but I'm afraid this might impact on our google page rank.