It's slightly more than 100GB and here it is: https://ipfs.io/ipfs/QmWSzgkftVrkh2859bGT44ahzoqcGhFkjsrQUtH...
(Note that the filesizes in the directory listing are all wrong -- that's the original index.html from loc.gov/cds/downloads/MDSConnect/)
This makes it a lot easier to use this dataset at e.g. hackathons, where a lot of people would simultaneously pester that LoC server, which already seemed pretty bandwidth-limited on its own when I downloaded the files.