No need to build special perches. I ordered some up from
http://www.summitracing.com or you can go to your local trailer supply shop and buy a pair.
I would use lowering blocks rather then pulling leafs out of the spring pack.....your looking at more wrap of the rearend with softer springs and wear on the u-joints.
You can drill the center of a lowering block to locate the center pin of the leaf spring pack and install the u-bolts and all on the rearend. Then with everything connected...but loose you can slide the rearend back to center it in the fender openings. Lower the truck and verify the tires are centered and then tighten everything. Your spring perch will have the stock pin hole that you can mark the top of the lowering block. Remove the block, drill and tap for a bolt which will locate the rearend to the lowering block
