Tech Forum

First, you won't find (as far as I can tell) any negative regulators that will take more than -40V input. Indeed, you will have trouble finding ANY regulator (positive or negative) that will take 36 to 75 VDC input.

So, since it appears that you have only +35 to +75 VDC available, I recommend something like the MIC28500 switching regulator (Digi-Key has them; http://search.digikey.com/us/en/products/MIC28500YJL%20TR/576-3969-2-ND/2764089 — note that these are surface-mount deals ... sorry!) to provide something in a voltage range that is easier for other regulators to handle (or you could just use two of those for the five and 6.5 volt outputs, and one for supplying the other regulators — note that one of these things can supply up to four amps!). So, I'd say:
• One MIC28500 for the +5V
• One MIC28500 for the +6.5V
• One MIC28500 supplying +12V (its max output) to the following:
Some sort of switching inverting regulators (like the LT3483 or similar) to convert the +12V to -6.5V, and -15V outputs.

Another switching regulator to boost the 12V to 15V, for example, something like the LM2574N.

If the MIC28500 chips are too expensive, you could just use one to supply +12V and choose other regulators from there (for example, an old run of the mill 7805 or 78L05 for the 5V).

I found all the above regulators by going to digikey.com and searching for 'voltage regulator IC.'

On the other hand, you could drop the voltage down to something easier for 'normal' voltage regulator ICs to handle using a resistor and a zener diode. So, you'd have a resistor of proper wattage and resistance in series with a 20V (for example) zener. Allowing for 2A of current (assuming we end up using inefficient linear regulators here, since the load is only 640 mA max) with an input voltage of 80V and an output of 20V, we need to drop 60V in that resistor at 2A, or 120 watts. Ouch! That's nuts! So, let's go back to the MIC28500 or similar.

Is there some way of getting a 'nicer' voltage input range beyond regulating it inside this power supply? That is, if you can manage to get the input voltage to a max of 30V, you greatly open up the possibilities for off-the-shelf voltage regulator ICs.

On the other hand, if you don't want to build it, I found that Acopian makes DC-DC supplies that could work — even if you just use one to convert that 36-75 range to something more friendly. The 48C5FT1000 supplies 5V and the 48C15FT400 supplies 15V, but they are pricy; about $188 each. TRC Electronics also makes such things, with various output voltages (trcelectronics.com).
 

Summary:
The options seem to me to be:
1 - Buy an off-the-shelf regulator(s), e.g., Acopian (expensive).
2 - Use some sort of down-regulator (Acopian, TRC, MIC28500, zener(!), etc.) to supply a lower voltage to the various end-user regulators, then have some number
(probably five; one for each voltage output) of regulators supplying each output voltage from the step-down intermediate supply. Use inverting switches for the negative; use whatever you feel comfortable with (LM7805, etc) for the + voltages (still somewhat expensive, and now you have to make it work).