I have run into the same issue.
I have the developer preview of Safari 6 (Beta) installed on Lion and now that ML is out, I can no longer get the uninstaller from Apple's Developer Connection Website. Like you said, all the links are stale and point me in the direction of the Safari Website with no download links.
All direct links to the Safari 6 Beta Uninstaller, like this one:
Do not work and say that your session has expired.
Unfortunately, at the moment, I have not been able to find a copy of that uninstaller or any older version of Safari to reinstall. Usually though, the beta version is just superseded by newer versions that will be coming out eventually or they will release an update for beta users, or reissue links for the uninstaller. Unless you can find the uninstaller somewhere, I would suggest doing nothing. Do not uninstall safari yourself or delete things, this might cause issues that could just as easily be fixed with patience. It suck to mess things up and make things worse when technically the Safari 6 Beta works just like Safari 6 for Lion.
I know it isn't the solution you were looking for, but everything will work itself out, either with Apple fixing things, or an update that just installs the newer version for you.
I hope that it helps.