2004 Dodge Ram Rear lift.

You're the third person in three days to want to do this. Rather than retype everything yet again, start by checking this post:

https://www.2carpros.com/questions/2008-chevrolet-silverado-lift-kit

I just finished helping a friend install new air bags on a 2011 Dodge Mega Cab that he extended the frame so he could put an 8' box on it. At 20 pounds of air pressure, it raised the truck about 1/8". Their purpose is to improve ride quality when fully-loaded. This is the second truck he put the bags on and he really likes them, but he isn't trying to alter ride height. Thanks to my training and experience, he knows better.