In reference to these (possibly overboard hackles) problems, I found a solution someone programmed; mt-wp-redirect, under “Redirect Moveable Type to Wordpress Template” here. You publish the template under Movable Type and it creates files with server redirect commands (and redirect codes for spiders!) which will route all those would-be broken URLs to the right place. Haven’t yet put it into effect for the expired Movable Type links this blog used to be at, but old links which wouldn’t have worked at this other blog now do.