I was able to, after some pain and gnashing of teeth and nastiness of language, get a build of Shuck with MWC68K and MWCPPC, including all of Thomas Wegner's changes so far. Yay!
The thing that sucked was Shuck sometimes loading the MacPerl Help file, and sometimes not. It turns out that the way it found the file was by looking for the location of the current process, and then from there looking for a file in the same location. Wonderful. Except that the ProcessInfoSpec structure requires you to set the processInfoLength field (i.e.., sizeof(ProcessInfoSpec)), because the ProcessInfoSpec spec is designed to be able to be upgraded in the future. And this field was not set, and so sometimes it would work, and sometimes it would not (apparently depending only on the humidity level of the surrounding air, or somesuch).
But it works now. YAY.