OK, I have Eudora 6.2, so I'm already behind.
Nevertheless, I correctly expanded the header, selected the entire message, and submitted it to the URL http://www.spamcop.net/mcgi?action=mhreturn . It came back with an error that three locations didn't match and proceeded to show me what was in those three locations. Unless I'm missing something, ALL THREE matched perfectly. Characters/case/numbers.
I then tried submitting via email per the Eudora procedure and Spamcop sent me a "Headers mangled" error message.
So now I've started the conversion procedure and don't know how to proceed or back the hell out.