I was about to suggest using factory 2" blocks from a 4x4 F250. Or, if you wanted just an inch of lift, you could use the overload springs spacer blocks from an F350 as lift blocks - that's actually just what I have in my truck, I moved my factory spacer blocks under the spring packs to use as 1" lift blocks, then used factory F-Superduty spacer blocks where mine used to be. New U-bolts are needed regardless of what blocks you use, and make sure you get the fattest bolts possible, for a halfton truck those would be 9/16" maybe?