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If you are looking for an IC which can be used for step up or step down supplies, I would suggest 78S40 from National Semiconductor. This can operate in the range 2.5 to 40V with a current capability of 1.5A. This could also be used in conjunction with discrete high voltage power transistors to extend both the voltage and current capabilities.
Another one is L296 SGS-Thomson switching regulator. This is a 4A device whose output voltage can be in the range of 5.1 to 40V.
Motorola also has a over voltage protection chip which could be used with a thyristor to have a 'crowbar' action.