Joe, the reason Mudcat's blickifier gets confused is likely because there's technically two URL's in an archive.org address and it's not sure how to parse it. I've had that issue on other websites before, though I'll confess I haven't tried it in awhile.

https://web.archive.org/web/20100412184834/http://www.roughstock.com/cowpie/songs/S/steel-magnolia/keep-on-loving-you

Doing it the old-fashioned way (<a href="link">text</a>), as tested above, works fine.