Yeah, I wish I had a good short cut I could pass on to you, but drilling out the spot welds is the way to do it. I think the rear is the worst, since it's so close to the cab corner.
Do you have a spot weld cutter? It makes it easier than using a drill bit I think. You can pick them up at Harbor Freight.
Here's a pic of one of my fronts, you can see all the spot welds along the length of the support, plus there are four on top of the channel that the cab sits on (far left of pic, around the cab mount hole) and two on each side of the support under that channel. Of course if you don't want to go this far, depending on how rusty your's are, you can always cut it in half and just weld the outer half in.
