GENERAL TECH By ZMan, Photos Courtesy of BigChaz
Flipping the rear spring hangers is a common how-to question in the forums. Primarily, it is done to lower the rear of the truck and is good for ~2". I have also heard it makes for more suspension travel and is popular with the prerunner crowd.
Step 1 (optional): Remove the bed of the truck. This will make things a whole lot easier, but it is an optional step. Soak all the bed bolts in penetrating lubricant a couple times a day for about a week to make removing them a little easier. Take out the taillights and loosen the light wiring.
Step 2: Cut the four rivets holding the hangers to the frame. This can be done with an angle grinder, air chisel (or air hammer), or a torch (be very careful if using a torch!). I found that an air chisel is the easiest way to do this. Make sure to have the frame supported with jack stands when you knock the hangers loose from the frame.
Step 3: Rotate the shackle/hanger assembly so it is upside down and bolt it back into place using 3/8x1 inch long Grade 8 bolts and nuts w/locking washers. Its also a good idea to get some paint on the frame before bolting them back up to help fight corrosion.
Anyone that has removed spring hangers knows what a pain it can be. But it's a simple and cheap procedure. Total Cost: under 5 dollars in bolts. Skill Level: On a scale of 1-10 I'd give it a 5. ~ TRS