Greasable Poly kits 52\'s in the front It's not tough to do, you'll use our standard aftermarket main eye kit, #GU37012 for the front and rear eye of the spring. If you can use our HD shackles, we just substitute the standard lower bushing assembly for a GU37012 (adds $4.00 to the shackle kit price) and you're done. Total with plates is $126.00. If you can't use our shackle plates, you get 2 - #GU37012 kits and the top half of our GU37015 greasable upgrade kit. Total without plates is $81.50 Either way, the top of the shackle will use a 1/2" gr8 bolt and both spring eyes will use 9/16" gr8 bolts. If you want to weld in a new shackle mount, use our fab-BA175HD bushing assembly spec'd to be 3.5" wide and you're set. Keep in mind we only use grade 8 or better bolts, our shackle bushings are an exclusive hard compound for longer life in extreme applications and we've even gone to a chromoly steel sleeve for even better durability. This is the good stuff.