I would get the Edelbrock EGR intake #3701. About the only option you have if it needs the EGR, which it will with emissions tests. It will also help you down low, where you need it. What is really killing you is the tire size and gears. This will limit what cam you can run. Go to big and it will be a worse dog and get worse mileage. You really need to consider swapping gears. Changing cams ain't going to help you any with 33" tires and 3.08 gears. You'll be fighting a loosing battle. The intake will help you now for sure but I wouldn't even think about a cam until a gear change was made.
The 1904 is nothing but a new Q-jet, and a great one I might add. You are correct, it is 795 cfm, but you have to open them big back barrels to get this. You will not find any carb to give you better mileage. I have a 1904 and wouldn't trade it for anything other than a new 1904.
I bet one reason you are drinking so much gas now is you are in the back barrels a lot because of loss of low end power.
Again, gears is what you need. Not much of anything you can do will help mileage or power without them. Assuming your truck came with 28" tires, stock. Your effective gear ratio is around 2.61 now. Not very good for low end power, or to help get a heavy 4x4 moving from a dead stop.
Just an opinion.