These are on the rear leaf springs. I was wondering if these were stock and if i could add more height to them. Many thanks!

 

Yep, factory bump stops/lift blocks on the 4x4's. Maybe just the off road packages? I'm not 100% there. As for adding to them, i assume you mean to lift the truck? well don't stack blocks, they get to be unstable. Best bet are true lift blocks and longer u bolts. Actually the best thing would be new springs to help eliminate added axle wrap by adding taller lift blocks.