Ford: 66 mustang, alternator voltage regulator, load test

Question
i have a 66 mustang with a 200 6 cylinder engine. the battery is not holding a charge, so i repalced the alternator, voltage regulator to see if that fixed the problem. well it didn't. i.m stuck and don't know what else to check. could it be that autozone gave me a faulty aletrnator or what do you think the problem is. please help

Answer
Danny, do a battery load test, if the battery fails replace the battery and also have the alternator re-tested to make sure is putting out 14 plus volts. ? when you plugged in the voltage regulator was it mounted to the body of the car? and was the battery disconnected? if not this will cause the new voltage regulator to burn out. let me know