Got down to it this weekend and cold set the rear triangles back into alignment. They were a few mm off, as noted, and now it's as good as new. The string measurement method, plus Sheldon Brown's leverage technique for cold-setting did the trick. One dropout was higher than the other, but that was due to the fact that the bend occurred at the brake bridge, creating a swinging motion.

Once that was taken care of, The chainline was better, but still off. I needed to re-space the axle, which was fairly simple and involved getting a new, thinner cone on the left side and adding a commensurate spacer to the drive-side. I dished the wheel about 3mm to the right, and I think all of my problems are fixed. This thing's ready to go!

Thanks all!