I know there has to be some hidden suspension package RPO code, like a heavy service package or something that makes the truck sit higher. The 99-07s are more noticeable that they all came on little 245s. Some look regular and others are like waayy up there, the front too. I know the HD frame is physically taller but still. I have an 03 1500 with 5'' of lift on 33s and there are some stock hds that the bed and mirrors nearly sits up with mine. the 07-13s are harder to tell because you can get like 4 different wheel combo sizes. But you can still see, every once and a while you will see a taller one. And does the z-71 package change anything? Like make sit 1'' taller compared to the zr-2 s10s that sit 2'' taller? F@*ds SD has the same thing, you can see an extra block in the leaf pack from the factory on some trucks. As far as the 14s and up, i haven't seen enough of them yet. It would just be nice to know. Its been bugging me for quite some time along with other people im sure.