Great to see you, mtnbke !! It has been WAY too long..
I beg to differ with you on one point: you stated that there is NO difference among differing levels of ST frames.
In 1987 that was true, as well as all prior years thru 1989.
I own 2 different 27" frame ST bikes form 1990: an ST400 and an ST600.
Both have cantilever brakes, but the rear dropout spacing is different.
The ST400has 6 speeds, 126mm rear dropouts. Serial # begins with "6"
The ST600 has 7 speed freehub with 130mm dropout spacing. Serial number begins with "0"
I also own a 1992 T1000 that has 135mm spacing.
That one truly IS the Grail for "our" size!!