Taking a poke at the links, most of them are broken because of the forum migration, not because of purging. I'd bet the majority of them could be found if we knew what the title of the thread used to be on UBB, which would have been ported over to vBulletin. But - again - the majority of them we have no idea what the title was, what much of the content was, or even who the original poster was...so we have no idea how to search for them on the new software to fix the link.
I would say we need to make a template for something like this.
{{TemplateName|oldlink=httpwhatever|reason=deleted, purged, ubb, whatever}}
So that it would suppress the old link so it doesn't display but not delete it entirely, and have a small (superscript?) "[post missing]" where the link would be in the text -- so that one day if someone magically stumbles over the original post the wiki could be updated.