Using just the shackle flip frame brackets like you can get from polyperformance and your stock shackles you gain 4" of lift. Offroad Design's kit you can buy 2" extended heavy duty shackles and gain a total of 6". Basically all you do is remove the brackets off the frame for the shackles, and bolt on the new ones. I had to drill the frame rivet heads with a 3/8" drill bit so the air chisel could chop them off easier. I'm still wanting to put a couple 1" welds here and there on them to secure them to the frame but they've done fine so far on the trail just bolted on. Pro's would be cost and ease of installation, also improved pinion angle without the need for wedges. Con's would be if you haul heavy loads or pull a heavy trailer stock shackles can get pretty much destroyed from lateral forces and the added weight of towing. But for a trail rig their perfectly fine. You might find a pro or a con concerning rear driveline length. I had to lengthen my driveshaft but it was in combination with a 14-bolt rear axle swap, which has a shorter pinion. Also under compression/droop of the rear springs the way the shackles move with the flip there's not a lot of slip yoke needed. You may not need to have the length of your d-shaft altered if you're using the same rear end the truck came with. Then again if you have really flexy springs it may need shortened just a little, my slip joint actually got shorter instead of longer on droop.
