A note on alternator ratings, they are rated via SAE J56 spec, which is 72 degree stabilized temp 6,000 alt shaft speed what it makes goes on the name plate.
so in general on most diesels the alt spins 3 to1 of engine, engine idle say 700 rpm is 2100 alternator shaft speed. so a 100 amp alternator will only make 100 amps at about 2000 engine rpm 6000 alt shaft speed. what you need to look at is the idle output that's where the truck will spend most of its time. Unless you like doing highway speed or fast idling the truck all the time.
