Same dealership as nissanparts.cc.
I've ordered parts from both sites and always had good luck. These were RB parts and 240sx stuff though, so I don't run into the out of stock problems.
Are they actually bolts, and if so, can you get to the tops of them from anywhere inside the trunk?
Maybe drill out the existing torched off stubs and make holes for a new bolt right through the unibody?
If all else fails, you can try torching the rest of them off and welding new ones right on.
Good job saving another poor old car. It'll be really interesting to see how much life you can bring into that thing. Almost looked like a skeleton out in that field.