We received some files from Release II.1 (early 1972) but it is missing significant components. After that time we have bits and pieces but nothing complete. We remain hopeful that someone has a distribution tape from the 1970s and we would expect that to have all the needed components.
Unisys has helped but not unexpectedly the machines we are targeting were end-of-life in the late 1970s and so they did not keep software for them beyond that time.