Power factor should be between 0.95 and 1
You would need a minimum 70kva transformer.
I would definitely check the NEC to see what the cushion should be. Say 80% equals 90kva, probably 100kva unit.
Another decision is what kind of S9 power supply. Since most high quality power supplies can operate from 100-240V inputs, I would try to have an unloaded supply voltage of around 230-235V to further increase the ampacity cushion.
In this kind of installation do people monitor the incoming wire temps?