There is another way to get the code, which is simpler, but will overwrite any existing files. There is a gzipped tar file /home/bah6f/nachos/nachos.prj/nachos486bare.tgz which contains only the eight files listed above, and all of the Nachos/486 code. If one untars this file in their top-level nachos/ directory, it will overwrite the files that need changing, and will add all new code.
There is also a tar file /home/bah6f/nachos/nachos.prj/nachos486.tgz which contains an entire Nachos distribution, with Nachos/486 in place and all files updated and ready to be used. This is simply the normal Nachos distribution with just the addition of the Nachos/486 code.