Any mp3 audio codec will do.
Divx3 did carry an illegal version of the fraunhofer codec thus it was removed from later releases.
Video should be fully backwards compatible.
There's a pack of codecs called the DefilerPak, assembled by a buddy of mine. It's got pretty much everything you'd ever need (and the best option when there's more than one for a filetype). It should cover the WCAs. As a bonus, it's a lot less sloppy than DivX is.