Interested in early Unix? It doesn’t get any earlier than this!
Apparently, the PDP 7 Unix was largely recreated from binary files. There is a bootable/runnable version. There are lots of tools and utilities, including two versions of the B compiler (which is how I found this.) One of them is written in C, so you can compile it. The other is written in B, like the original.
And there are other early versions under the same person’s (Warren Toomey) account.
This should keep me busy for a little while!