2003 avalanche cladding

Hello Avalanche gang💪🏽. I have a 2003 Avalanche with cladding and everytime it rains or I get a carwash there is water coming into the back bed. It leaks from the rear tailgate area and the midgate area. I changed the back panels too truckxedo roll up cover and it's leaking alot less but still...

I have been reading about the benefits and best of both worlds with a suspension and body lift combos. Close to 200,000 miles on original shocks so it’s definitely in need of new ones, plus want a little more clearance without messing too much with Center of gravity. Nothing terribly high, but...