I haven't tried Unstuffing it in 5.5 (Although for me it always works), but the .sit file in the Macintosh Garden unpacks just fine with StuffIt 3.5. If you want, I can give you a disk image with StuffIt 3.5, or I can give you the disk image of Enchanted Scepters itself.
For StuffIt in Basilisk, you should be able to use StuffIt Deluxe
or Expander 5.5
just fine. I can give you my working copy of StuffIt for Basilisk as well. It unpacks almost any .sit archive you will ever find, and I installed the plugin which conveniently lets you ALT-U (is ALT the Option key or the Apple key?) to unpack any archive you have selected.
*EDIT* Here is the disk image for Enchanted Scepters
(just unpacked them)
Here's the disk image for StuffIt 3.5
. This one is for System 6.0.8 in Mini vMac (not sure if it'll work in older systems). It unpacks some archives you will find.
Here's the disk image for StuffIt 5.5
. This one is for Basilisk II, and unpacks pretty much any archive you will find. Place the extensions in your System Folder to get the Magic Menu (the aforementioned plugin), which gives handy and easy shortcuts for .sit archives.