The only time you would/should ever reach peak current (78 amps) would be if ALL the servos were locked rotor/stalled SIMULTANEOSLY. The chances of that are two, slim and none.
The next problem you have is that the motors have different voltage ratings. if you run at 60 volts, the rated speed of the higher voltage motor will not be reached. If you run at the higher voltage, the lower voltage motors could be oversped or perhaps burned out due to overcurrent from the higher than rated voltage. Running separate P/S's would fix that problem and solve some of your current concerns.
In your combination, if any two servos would be running, you'd see between 7 and 12 amps depending on which two were running. Load would spike this up but not anything of much conseqence.
The only issue of not enough amperage will be at high current demand. Either the motors will not pull rated current and thus rated torque or the voltage of the P/S will dip as you load the supply and it can not supply current in the amount asked for.
As an approximation, a peak current capability of 60%-70% of your absolute max current draw potential should be adequate for most of your needs. More is better of course but it all depends on how much you want to spend. When all things are considered, you will not be disappointed if you build a bigger as opposed to a p/s that is too small.