If it makes a difference, I'm running 10.5.
I've been looking for quite some time, but I can't really seem to find anything.
I'm not necessarily looking for identical usability. I just miss the old "look and feel".
I doubt it for two reasons.
In order to create a skin you would have to close down virtually every native process (Finder, Dock, whatever drives the menu bar) and overlay these with custom built applications. I don't even know if that's possible not to mention speed would probably be shot in the foot.
Your best bet would be to simply run a PPC virtual machine.
There is Magnifique but it seems to be all but dead. You can download it from the download link on i use this. But be ware it seems that it breaks Snow Leopard. Only use it with Leopard. Also, it seems like the server that held all the themes is no longer available and so you will have to search for themes via Google. But I couldn't find anything.