Spring relocate rear mount questions

Ok. So well into the spring move and wheel tub process. Everything is going good so far. Got my kit from Bill with the extra holes drilled. (This is one fine kit.) Better then the others I have seen. If you are planning to do this mod, Talk to Bill first. You cant go wrong. Well anyway the rear mount I have removed and am in the layout and planning stage. The problem is that the hole that is in the frame where I need to mount the tube in the frame, is the hole that the rear bumper shock absorber is mounted to. It is so rusty. Now keep in mind that when all mods are done, I will have the whole car media blasted. I wanted to do these mods first so it could all be blasted and coated at the same time. I will replace floor pans after the blasting is done. has anyone removed these befor. The frame has a captured nut in it, and I think this will make the area stronger for the tube. Is the shock under pressure? can I just torch it out. I will have to make mounts for the bumper. I will most likley use fiberglass ones. I sent a pic. any comments or sugestions on removel would be greatley accepted. throw money