Which alternator 60A or 46A?

My '71 Dart GT (318, auto, A/C) is in need of an alternator. NAPA shows a 60 AMP or a 46 AMP available. What was the factory alternator rated at?

The car has no extra electrical additions other than AutoMeter electric gauges (water temp, oil pressure & voltage) and a tachometer.

Thoughts?
My old man always said "Go big or go home".
It applies here.