I have a 4.5" Icon on the truck. i think the blocks were the 5" flat blocks. its hard to see in the picture, but if you look close you can see how much it shifted towards the rear. I do have the carrier bearing spacer kit, but havent messed with that yet. Do i need some sort of shim for the rear block. ive been looking around for a while I just want to make sure i get the right thing before i buy.