Removing the inner half of the stock tubs isn't so hard. Just make sure you make your cut to split the tub straight and not at the existing seam. Cutting the inner out from the floor pans is easy but you'll want to cut them in a line that will allow you to weld them back in and not have to use much of a patch around the front and back. Slow and steady, measure twice cut once. Welding them back in now that's a bit more trickey. Make short welds and alternate from back, middle, front making no more than one inch welds. Other wise you'e going to warp the metal and it will fight you the rest of the way.
I'd suggest tacking the bottom to the frame rail in three places, front, middle and rear. Then tack the top to the trunk brace and the cross brace behind the rear seat. Do this first and then continue stitch welding the inner half of the tub in place to the frame rail. Slow and steady wins this race, rush any part of it and you may have a mess.
Dan
