What is the point of the second alternator, if I may ask?
Do you have one PTO (two alts run on one big belt in a triangular configuration) or dual?
I have a new Beta 60 with dual PTOs precisely because I wanted two 75-90 amp alts to charge my 850-1000 Ah banks. For reasons of heat, cost, wear on the crankshaft, "thieving" of horsepower, and redundancy, it's easier to contemplate a pair of sub-100 amp alternators than one big 'un. Also, I have extensive solar
charge sources, so the alts will only be, unusually, the third line of charge sources as I intend to only run the engine for motive power. So the alts will be set up, unless I'm at anchor
for five cloudy, windless days, to provide a "finishing off" charge, rather than to recharge a deeply discharged bank.
So it's a case of working backwards from the application to determine a right size, I think. The size of your bank is irrelevant until you tell me your daily draw-down and whether you are going to stay on the hook all the time, etc.
As for make, I favour Leece-Neville because they are popular in Canadian 18 wheeler trucks!
I think Balmar
is a little overrated, or rather, I think I can do what they do with external regulation more effectively than their price
premium can justify. Just my opinion now; it's subject to further persuasion.