new brake is apparently the answer from the miyata/specializing touring yahoo group. even with a simple kool stop bolt on pad it didn't work.
here's what will, it seems:
"shimano cx50/cx70 will work. use the thinnest conical washer. pair the brakes with koolstop thinline pads if you need more clearance. i have this set up on my '83 expedition"
thanks for your help!