So the idea here is to actually re-write the url's into spider-friendly url's? hmmm... would be a heck of a job updating your forum I'd think, tho I may be wrong.
I would suggest something else, to either create an 'archive' script that would give a seperate page for spiders to crawl like vb does, or do something like Micah did for ubb.classic and write a script that can make it
appear like the urls are spider-friendly
http://www.praisecafe.org/boards.php looks like this to the spider:
http://www.praisecafe.org/boardsleaving all forum files untouched:
http://www.praisecafe.org/ubbcgi/ultimatebb.cgihttp://www.praisecafe.org/ubb/ultimatebb.php