Yeah,I tried that route at first too,and ended up dissapointed..
When I decided to put rockers and "floor patches" on my '72,I decided to rip both front seats out,and get a large sheet of 16 gauge galvanized steel,and "built" a whole new floor from the firewall to the "step" behind the seats..
The original floor only had a few spots with holes about an inch or two in diameter,but it had cracks where the seats and seat belts bolted in,so I decided to go with one "big" patch,instead of 20 little ones..
Back then I only had torches,and ended up using 1/4" bolts and nuts with fender washers to bolt the metal in with,along with pop rivets and a few brazed spots,after I welded up the cracks in the seat bolt holes and seat belts..
It looked rather crude,but not many people look under the rug..

--and I could feel how much stronger the body felt after that was done ..my doors no longer threatened to pop open when I hit bumps,no more rattles either..I kept that truck 8 more years and it didn't rust again after I was done with it--when I got it I was so disgusted with the rot ,I was ready to part it out..
Ever since my first rust repair episode when I did "spot repairs" and ended up with a patchwork quilt floor,I have since gone whole hog and do the entire floor over..and I lap the new one over the old,only cut out the rotted areas..some might call that hack,but I feel it ends up "double strong" that way..might not look "factory",but I'm not that anal..
I did my '75 2wd K5 that way,and a '79 Bonanza..