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You can use e.g. the LM350 adjustable voltage, 3A regulator. Two resistors are needed to set 12.0V output. Make sure to use a good heat sink : I would prefer to add a dropping resistor before the regulator, to get ~15-18 V to regulate. The dropping ~22 Ohms, 100 W resistor will dissipate the large power before you regulate.
Another less lossy solution is to buy a DC/DC converter; there are versions with 40-70 V input and 12 V regulated output at 2 A load. They offer >75% efficiency, so less heat to dissipate. Only the size is bigger than the first version.
I wouldn't recommend a linear regulator for that much power. It gives you 96W to dissipate which is a lot. The LM350 cannot do it - it has 1.5C/W junction to case so even with an infinite heatsink would exceed the maximum junction temperature at room temperature. Even if you have a series resistor you still have to get rid of the heat. Look at switching regulators such as the LM5088 or TPS54360.