The biggest hints I can give anyone is that MPW hates the XPLUGIN_API(?) macros, it needs(likes) .h files with a #pragma export in the right place, and you build it as a shared lib, for PowerPC, binding to carbon..... the rest is easy. ;-)
One other thing: Use: /Developer/Tools/SetFile -t TEXT <.h and .c files>
Use that command on all the SDK include files and source code files, this sets up some OS 9 style resource forks with the correct file type, if you dont do it MPW will spit the dummy claiming that it can't open the file cause it "isn't of of type 'TEXT'" ... You can edit the files fine, but you wont be able to use the Makefile wizard or the compiler or linkers.