Do not be afraid of the shackles, they are a very well built part and worth every penny. If you are looking for a truly performing part that will augment the flexing ability of your truck while still retaining that scale look and feel of leafsprings... Then you have bought the right part. Those SuperRides look to be 80mm, right? If so, that is exactly the same shock that the Marlin comes equipped with, and I have mine with both the Revolver Shackles and the Z-boxes and I can tell you that the difference in flex was day and night.
Now, keep in mind that if you want your build more towards scale looks and performance, you will be separating yourself from that by adding this parts as they are more intended for trail/rock-ability than scale looks (at least that is my take on it).
Regarding your build... Man, I'm really digging that color and the overall neatness of your build. Those bumpers look so sweet on it and the bedliner paint... Damn, really nice build. I looking forward to the interior and scale accessories. Keep it up, cause when you get the chance to put it through its paces, that's when all the gratification will be felt. Enjoy the build.