Very little left now - all the vertical bits are gone that faced Sudbury Street. Two "cells" are left closest to the surviving part of the garage, and the bottom most floor.
It looks almost as if the artist has smooshed India Street and Broad Street together - you can see the One India St. apartments right behind the custom house, but immediately to its left is 33 Broad street. The Grain Exchange building is shown sorta where the Insurance Exchange building is...
There seems to be some oddities in that 20th Century Boston image. The Grain Exchange building is not next door to the Customs House as it appears in that drawing.
Could you help me understand this point in a little more detail? Do you mean that some stations could have extra tracks laid across space currently occupied by the low level platform? Thus therefore you could not build a high level platform in the current station geometry?
Bonus post: I had nearly forgotten about the YMCA proposal for Parcel 6, cancelled due to cost. Maybe someday with the garage gone something could happen here:
May as well add some images of the New Center for Arts and Culutre that was supposed to be across from International Place. I still recall it being described by someone on the old forum as a "crushed egg carton atop some popsicle sticks". This parcel isn't too bad as it is today, unlike parcel 12.
The dark colored stuff hanging on the corridor from the lifts to the old offices hangs way down to the street, which makes me wonder how they intend to demolish it: