A voltage regulator? There are many designs for low drop-out regulators out there. Which ones have you tried? 70A is a fair bit of current but not ridiculously high. Given the option a switch-mode type would have the lowest losses but dropping a couple of volts is certainly possible using a linear type if you don't mind a big heatsink and a fan (or a really big heatsink and no fan).
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Difference between input and output is prety small, only 2V and have to supose that input voltage drop at full load will be very small.
Depending what mean "regulated" 12V - what % is allowed for application, one simple way and cheap is to put 2 or 3 series power diodes to obtain 11.9 - 12.4V output voltage. Large heatsink may be needed. If is not acceptable you'll need a converter, maybe with transformer 1:1 or even slightly higer to overcame this small input-output voltage difference and by PWM control to obtain a very stable 12V output.
I wondering why/if you actually need a regulated 12V.
Most of the current consumers I can conjecture that have a nominal voltage of 12, are actually intended for use in automobiles, where the system voltage at which devices are expected to operate ranges between 8-ish and 14.5-ish volts.
Car battery voltage may be over 14 Volts at no load, and below 12 volts when partially discharged and under heavy load. 13>8 Volts has been a widely used full charge voltage for automotive batteries and I have seen higher settings.
Bill
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