32-bit PowerPC ABI used in the macppc arch

Hi,

I am working on converting ofwreal.S to 64-bit and I'm basing the stack
(section 3.2.2) off this document:

http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html 

I haven't found a 32-bit version of this, what did OpenBSD use for macppc?

I have in the meanwhile gotten a book called "Mac OS X Internals" by Amit
Singh and it's a good book, it has a section regarding the 32 bit stack.  
It talks about a Darwin ABI, would that help me any in OpenBSD/macppc?

Any help is appreciated.

Regards,
-peter