I forgot when I made my 4" blocks (1/4" wall 2x4 box tube) that I also swapped the u-bolt plates to tri-5 chevy plates! (sorry 'bout that!) I used an allen bolt on one side for the pin, and started with a 1/2" drill hole on the other side, but it was so long ago I don't remember if the hole had to be bigger or not. FWIW I don't recommend the 4" blocks-- your scrub line is below your rim, and if you have a flat-- well....not good. no one will recommend this-- but when I cut my coils I used a torch (eeeek!!!!!) and a prybar and cut them in the car ! I've never felt the ride was compromised due to the torch. I'm not saying it was the right way, and I don't think anyone here will condone it, but it works. if I ever get the car back on the road (if I don't sell it) I already have 2.5" dropped uprights for it, and I'll start over with uncut springs. On the rear, I always wanted to get new, lower leafs, and then blocks to finish it off.