They are almost the size of T-105's so I would guess 200ah's at 6V t the 20 hour rate for each. This translates into 600 a/H's at 12V...which is quite a nice sized bank.
Without the actual NAPA spec # and detail sheet it is tough to be accurate but between 180 and 200ah's should be in the ballpark for you. One rule of thumb is that if they weigh in the ballpark of 65-68lbs...my estimate should be accurate.
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