My 345 owners manual says 2,000 lbs. gvw with a 200 lbs. hitch weight is the maximum. Anything over 1,000 lbs. must have brakes to assist in stopping. The Airstream owners manual and the Chevy manual say the same thing. I imagine this is true for all the chevy P-30 units. Although I imagine the 20' units could pull more since they are 14' shorter and that much lighter.
Since you have a Banks system, you might be able to exceed that number by just a bit. Keep in mind that Banks gives you more engine power but no additional braking power.