I dont know much about the boost question but if you look at a gear ratio vs. speed chart/graph you can easily pick your desired gear ratio.
My guess with 33in tires and overdrive trans you will probly be able to go somewhere between 4.11 and 4.56.
As far as I know, they dont make any lowering kits for 4x4s.
Does it have a lift kit?
If it does for example, if you have a 6in lift and you want to go lower you need to get a 4in lift effectively lowering the truck 2in.
If you really want to get creative, you can bolt angle iron under the frame and lower your spring shackle mount on the frame to your desired ride height.
If you installed a drop shackle with the flip kit you can just reinstall the factory shackle. If you still have the stock shackle you can add a leaf to your springs or get a shorter than stock shackle. I have seen them before but dont know where to get them. Other options is to shorten your...