1972 dart alternator pulley shaft question

battery showing 12.65 on the volt meter engine off . stays the same running at idle , when i put it up to fast idle on the carb , it's reading about 13.10 ish . full throttle tops out at 13.35 but the alternator gauge at idle was fine , then went all the way to the charge side again at fast idle . it definitely didn't do that before changing the alternator today . it would go a little to the charge side normally on startup and then quickly back to center . i don't know how long i was driving it with the bad alternator , but it cranks real good and starts right up . any thoughts ? anything i should be checking ? anything to worry about ? i need the car in the morning .