Chris Fenton here - someone did actually send me an 80MB 'disk pack' with software, and I was able to modify a super old disk drive to actually read it:

http://www.chrisfenton.com/cray-1-digital-archeology/

And thanks to some awesome help from others, I was able to actually recover a copy of COS (Cray OS):

http://www.chrisfenton.com/cos-recovery/

Andras Tantos and I have been collaborating on this together for a while now, and he actually has a downloadable Cray X-MP datacenter simulator he wrote, where you can run the COS image I found:

http://www.modularcircuits.com/blog/articles/the-cray-files/