I used a grinder to cut the heads off the rivets and knocked them through with a hammer and punch. Then I cleaned up the holes with a small die grinder. A plasma cutter or air chisel would have been easier, but those are high-dollar tools. Fishing the bolts through the frame with the factory Suburban fuel tank in place was as much fun as lemon juice in your eye. I finally devised a system whereby I wrapped a small wire around the bolt threads and pulled it through. I found out later that Draw-Tite makes a coiled wire pull (PN 55393) perfect for this.