Thanks for the idea intron! I found some SIS housing at an LBS that caters to old bikes. It fit perfectly. Actually I used a combination of standard shifter housing and the SIS I'd never have gotten the stuff to work at the BB without something as thin as that SIS. Here's a picture of the final result (in which you can just see the crank adapter that put the Shimano 600 in there) -- more pictures when I finish!