i dont really understand the "leveling kit" our trucks already sit virtually level. any rake in the trucks is designed to compensate for loaded cargo areas.
something like the ones mentioned on this page: http://www.wheelersoffroad.com/96024rundstrlift.htm would be pretty good. not my cup of tea, but for bang for buck, they are probably pretty good. i have no experience with them, or second or third hand accounts either.
they are another excellent source for accessories, and come highly recommended!