Those kits for modern trucks are for use with the strut type ifs or solid axle with coil spring, the "blocks", which are actually spacers, mount to the top of the strut/spring. Dealing with a leaf spring solid axle is a different story, virtually all lift kits for those use either deeper arched springs, or longer mounting points at the frame for the front.
The kits I am talking about are for leaf springs. Don't put words into my mouth. On higher lifts you are correct, but on 2" or less, typically blocks are used. I have seen these kits, but apparently that's wrong. Blocks are easy, cheap, and reliable with 2" or less lift.
