So basically the vB conversion scripts renumbered all the threads because they have new database schemas. That's why it's not just straightforward. The reason I upgraded was the site was getting "hacked" a couple times a month because I was running a version of vBulletin that had security flaws. It was either leave things the way they are and allow the site to get hacked or actually upgrade. I chose to upgrade. Yes it sucks all the old links are now broken, but it is what it is. I still have the old database so I can attempt to create a lookup between old threads and new and manually build an htaccess redirect, but that will take some time.