My parts fische has it listed for the 85-89 911 and lists for $12 (ea.) but I don't have the fische for 84 and earlier although it's probably the same.

When you do this try and get some pics so we can put together a tech article.

While we're talking part numbers and interchangeability, the bracket that mounts the 924/944 rear sway bar bushing is the same one that mounts the 1302/3 front sway bar bushing. That's more just trivial.