Mike:
I agree....I've looked at a few pictures of them and, if you're building them from scratch and making them fit just right, then the caster shims probably aren't necessary (although I wouldn't necessarily rely on slotted holes in the angle mounting bracket to hold everything in place the way you want it if I were home-fab'ing them).
Jack:
These gizmo's have been around forever, but few people ever thought of installing them. They look goofy on an open Dune Buggy, so some people opted for a more elegant brace which was always visible (kind of like the "Hairpin" braces on early Ford Street Rods).
The purpose of this brace it to keep the wheel ends of the front beam from jiggling front to back, thus, stiffening the front end. What your installed sway bar does is try to keep the body left-to-right-horizontal more in line with an imaginary line drawn along the length of the front beam, across the front of the car. Two different things.
These brackets should reduce or eliminate the "Shudder" that happens if you go over some train tracks at, say, 35mph (Wham! - shudder, shudder). They will also improve some handling, but you have to push them quite a bit before you notice the difference.
gn