Ask for the payload when you talk to the air taxis...I thought a Beaver might be around 900 or 1,000 pounds, but I could be off a little bit.
On a drop hunt, figure 2 guys and 300 pounds of gear would get you a REALLY comfortable camp - could take 2 tents, different types of food (i.e., not all freeze dried), extra clothes, and other extras. You can do the hunt with a lot less gear, but why scrimp when you probably need to pay for the full plane anyway. And, scrimping on gear (let's say you went in with 150 pounds of gear total) still wouldn't allow you to fly out in one load if you get a moose.
Good luck, nothing like a flyout hunt in Alaska. I'm planning my 10th flyout in the past 13 years for this fall, and every trip feels like a new adventure.