Best way to separate pinch welds

Thanks for the suggestions, I really cant afford another tool so I'm going to try drilling the side that is the trunk extension with a regular drill then switch to a flat bottom drill trying not to pernitrate the outer layer. Maybe look at one of those spot weld drills but they look to pernitrate the both layers.
I completely agree that the little belt sander isn't necessary, and if there's anybody that can relate to not bein able to afford something, that's me. But harbor freight has one for 25 bucks. Next time I go to Macon, I'm gettin one. If you decide to, I can tell you from using one to get the 80 grit. The 60 and 40 grits work like gangbusters, but wear out real quick. Whatever you do good luck with it. You'll get it done, regardless which method you use and you'll learn somethin new in the process and that's priceless.