Making a rally dash frame

I'm going to cut a '74 dash frame to fit a rally bezel. What is the tab just above the radio used for (circled in pic)? I don't see a need for it and don't plan to leave a tab there when I cut mine.

Also, I'll have two 3/8" holes to seal to the right of the climate controls. What's the best way to seal these holes if I'm going to powdercoat it? I'm worried that the heat from welding will warp the frame and I don't think I can use a filler if it's going to be powdercoated.

Rally Dash Frame.jpg