Good luck. Removing the rear hanger rivets was one of the toughest parts of my axle/rear leaf spring swap. I used an angle grinder to remove the heads and then tried to push them through with a hydraulic hammer/punch (no dice). I then used a long rod as a punch and a sledge hammer. That combo flexed the frame away from the hangers and the hangers fell free. Continuing the same approach on the remaining rivets caused the exposed shaft to mushroom out. So once again I had to attack them with an angle grinder, removing more material until they were flush with the frame. After that, the long rod/sledge hammer finished the work. Each of the rivets went ballistic when the finally broke free. I have read that others have not been that tough, but mine were.
2000 4X4 Ranger, F-150 9.75 w/ 4:88's, Dixon Brothers Racing Long Travel Kit, Giant 64 Kit Long Travel Leaf Spring Kit, 35X12.50 BFG All Terrain KO, Custom front bumper w/ LightForce HID's, Rocky Road Outfitter's Super Sliders, Cobra CB & Alpine head unit.