[biggsteve97]

Those cast iron blocks are stock on only the 4wd 99-06 GM 1/2 ton trucks. The Z71 package is just 46mm shocks(the standard are 42mm),skid plates(usually metal) behind front bumper and under transmission, and a sticker. They use the same springs and torsion bars. This has not changed since the inception of the Z71 package on the 4wd, there might be a difference when they started using the package on the 2wd a few years ago.