Raising Alternator Voltage
The output voltage of a common vehicle alternator is controlled by its internal rectifier/regulator module (although external regulation was once common, it's not now). Opening the casing on many modern alternators to replace its regulator with one of the target voltage is not an easy task; putting it back together can be even harder; when the alternator's rectifier circuit failed in my 1973 car, however, I managed to open the casing and replace it.
The added problem is fitting your replacement regulator inside. After disconnecting/removing the original module, you may have to hardwire from the alternator to your externally mounted replacement regulator.