You can sometimes avoid the cutting by drilling the hole a little bigger (the new nut will never be perfectly centered and you need a bit of space away from the threads for the tack weld), cleaning the inside area of the frame with a small, bent file, then fishing a new nut through to the hole with a wire. Then tack weld around the edge.

97tj, Shaved Ford 9 rear, 4:10's, New 35x12.5 BFG KM2's to test!, Warn x8000i, ARB's, Quick Disco's, Hand Throttle, & it's my DD. smile