Alternator Capacity for 1968 Dodge Dart 270/SL-6
here's a remanufacturer's test print out that NachoRT74 posted on moparts.
Its was the box with a late 'square back' alternator.
Notice how the output goes up with rpm. (that's probably alternator rpm shown).
These are amps at 13.2 Volts.
and FWIW here's a Dodge truck FSM specs, probably late 70s or early 80s