Going with a lift will not have any factor on making the truck squat more in the rear so adding air bags to a lifted truck is the same as adding to a factory height truck. All you're doing to the rear is inserting a larger block to increase the height.
And a drop hitch is for a bumper pull, not a 5th wheel.
I'm not to sure whats the max height you can go and still be able to tow a 5th wheel. You're lifting the rear 4-5" from stock after you install 35" tires depending which 35's you decide to run.
Here is a 4.5" ICON lift I recently installed.
Factory 20's and 35" Mickey Thompson ATZ
Same wheels as above on the side of my truck. 7" ICON on 37's
35x12.5R20 Toyo Open Country's
