Here's a quick fix for PithHelmet for Safari 1.2:
Open /Library -> Application Support -> SIMBL -> Plugins. Control-click on PithHelmet.bundle and select Show Package Contents. Open the Contents folder and from there, open the info.plist file in either TextEdit or Property List Editor (if you have the Dev Tools installed). Find where it says MaxSafariBundleVersion and change the value to 125. Save and restart Safari. That's it, now PithHelment works.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040202172210471