on north american trucks the total system is 12 volts in 99% of cases
not sure about european trucks maybe they are 12/24 or straight 24 volt systems
the leece neville/prestolite 110-555jho alternator is a large frame 160amp unit
12 volt nominal, it uses a piggy back regulator that is easy to remove and fit a
proper 3 stage controller such as the balmar, xantrex, amplepower, hart, etc
and there are at least 2 other controllers made in england that i am aware of
that do the same job.
the 110-555jho uses large ball brgs front and rear, has brushes that are user accessable without removal of the alternator or a complete teardown, the unit is rated at 160 amps at 70 degree's but figure on ~120 continuous output hot.
they use a standard 7/8" bore pulley so you can get any size pulley you want to fit
them easy enough.
they are about 54% efficient at charging 12volts nominal, which is about as good as any alternator, but
should you decide to go with a 24 volt bank, i can get you well into the low to mid
70's efficiency with a bit of modification. i have a prototype system that is doing quite well at very good efficiency generally not seen with automotive alternators.
the beauty of an belt driven engine/alternator setup is you can dial back the rpm
when you are topping off the battery and reduce noise and fuel consumption as well as increase the longevity of the engine in most cases.
also with a bit of work, one can fab up and fit a heat exchanger to the exhaust and make domestic hot water as well, which is a very good use of waste heat that would normally go up the stack anyway,, everyone needs domestic hot water for laundry, washing dishes and a hot shower is something that is nice as well.
the last thing i would want or recommend would be a 3600rpm AC genset, screaming for hours to provide power for a charger, to charge batteries so that you can then
power inverters to power loads later. too many conversion steps and your efficiency will be dreadful even with the best of equipment.
eliminating conversion steps enable you to use less costly equipment and still get better efficiency overall.
don't get sold on "single" point efficiency, such as "our charger is 98% efficient"
(which it likely only is 98% efficient on a cold day, at a specific load, at sea level, at a specific baro pressure, if you hold your mouth right.. etc, and be well off that level of efficiency in the real world anyway)
what you should focus on is "total" system efficiency, learn what it takes to improve the total efficiency. small things sometimes can make significant improvements in total system efficiencies.
it is the total system that consumes the fuel to produce kwatts that you will consume.
and remember each watt conserved is worth a lot more than each watt generated
as ben franklin said, "a penny saved is a penny earned" in this game it likely
is "a watt conserved is worth 3 watts generated" maybe more, but likly not much less.
as for desulfators, forget them!
you got new batteries, so use them properly, charge them properly, and it is unlikely that you will ever have a need for a desulfator. There is ample evidence that they will not improve the lifespan of new batteries and some evidence that they might even be detrimental.
if you are set on useing one, use it only during your equalization charging, the rest of the time just do the standard 3 step charging, keep a log, and learn to use your temp compensated hydrometer.
good luck
bob g