"Battery with engine off - 13.6
Turned engine on
Idling with no lights - 15.0 steady
Turned on parking lights - 15.0 steady
Turned on headlights - 15.0 steady
Turned on headlights and turn signal - 15.2-15.8 cycling
No lights, turn signal on - 15.2-15.8 cycling "

Does not sound to me like you need an alternator. As much as old timers may disagree, 15 volts it just about where you want it. These newer batteries can take it. To charge the old batteries of the 1960s that hard would cause too much water loss and you'd have to feed it every couple of day. Not no mo.

If you are charging at or near 15 volts and have trouble starting or anything you either have a bad battery or a fault in the system draining the battery. And don't forget, newer cars do drain the battery constantly to maintain memory.