JavaApplicationStub from SL for PowerPC

Issue a file command on that particular file. If it comes back with PPC you are golden. If it comes back intel only, go into the jar bundler app and see if you can't build a stub that has PPC in it(or go back to an earlier version of the OS and use that stub)

As per 32/64 bit, all PPC java is 32 bit only. For Intel machines, it depends.
The best way forward(if possible, depends if your app uses any JNI libs or not) is to include a 32 bit and 64 bit stub. That way 32 bit intel users can use your app while 64 bit users can get the extra speed bumps that come with 64 bit apps without having to intervene. They can also run it in 32-bit mode if they go to the finder, click your app, click get info and check the "run in 32 bit mode" button.

If you want to ONLY run it in 32 bit simply don't provide a 64 bit application stub. If you want to only run in 64 bit, provide an application stub that has ppc and intel 64-bit intel arcs only(you can use the lipo to get rid of the unwanted architecture(s))