I'm pretty sure the crane bucket was 2000 gallons but we had it restricted to about 1400 or so due to the altitude. You can see the center strap in the photo that keeps it from filling to capacity.
With the Firehawk we use a 660 gallon to full capacity at sea level.
Ooops. My bad. We use an 800 gallon bucket at sea level and cinch it down to reduce the capacity as we head west and up into the higher altitudes.