A little sanding will reveal where the spot welds are. Or you can gently pry the angle strip away from the bedside and drill where the strip stays attached. But a cleaner look would be to remove the spot welds with a spot weld cutter from the angle strip side (don't drill all the way thru the bedside), then put your carriage bolt holes on an evenly spaced pattern. The factory spot welds probably won't be evenly spaced.
Or if you want a more original look, have someone weld the angle strips on for you. You might even find a fellow Stovebolter in your neighborhood who'd be willing to help.
