I used the Blair cutter with the spring-loaded center point. It looks like a mini woodworking hole cutter. Circular with teeth along the cutting edge.
Locate the spot welds, (sometimes using a light grinding pass or roloc scotch-brite pad), center punch the center of the weld, drill using the punch mark as a locator, stop drilling when you are through the top layer of metal, separate layers with whatever works best for you, chisel, old screwdriver, etc.
best to have extra cutters and center point on hand, depending on how many welds you are cutting. I used it to replace my floors and front clip on my 69. several hundred welds. personally, I wouldn't use anything else.
