Should I switch out the tires ???

As everyone says here, the process is somewhat precarious, and anything you can do to prep things best as possible before you are laying on your back under the truck is time well spent. For me, given you have to line up four bolts/holes on several different planes without knocking the fished bolts back through the frame holes, my main suggestion would be to prep the one 2" x 2" spacer onto the tiedown beforehand by super gluing it to the tiedown bracket. If Torklift needs a spacer at that point, it should be tack welded to the bracket right out of the box. Wrestling with all the above while the spacer is sliding around on you (as I did when installing the first side) is yet another degree of freedom you don't need when trying to execute this task. Good luck with your outcome.