doing a MML will relieve your vibes. you will be able to ditch the t-case drop.
i've never measured the diameter of my JKS pucks, but they have a thin lip that kinda fits over the stock body mount bushing. i think it more or less keeps the puck centered on the body mount......you could go from there. other kits don't have that lip, they just sit on top of the bushing and are basically the same diameter.
as for the bolts....take a stock one out. measure it and add 1.25" and that's the bolt you need.
aluminum is fine to use. the M.O.R.E. kit uses alum.
the blocks are not all the same size though. the ones to the rear around the gas tank are smaller in diameter IIRC.
the bolts are not all the same diameter either. pull some from the front/middle and pull one from the rear. don't remember the actual size but i know there are only two different sizes.