For the Buick rockers in the photo on Mace's website the pedestals are welded to the metal plates, do I need to do this here or was it supposed to have been done before they left?

Good question. To improve product quality, the design itself has changed such that no welding is required (on our end). The only thing that you need to be mindful of is that the retainer block plate is installed first then the rocker support blocks. While the retainer block plate may have the potential to slide up and down the support blocks, in practice it's not an issue