So far, everything you have shown is available new or used for replacement parts. The best options on the floor would be the full length inner rocker and floor section. That piece extends from the rocker towards the middle of the floor about 5". The floor pans will cover anything forward of the seat to the firewall. The floor area under the seat can be patch with regular sheetmetal as needed. Or you can cut that from most truck cabs, then just add the seat re-inforcement from the blazer floor. The windshield pillars can be cut from any truck. Outer rockers, door bottoms, etc are all available new.
So far I haven't seen anything that can't be patched up on yours. It just depends on what you want to do. Starting with a good solid tub is great, but not the easiest to find or get delivered. For inspiration, check out this build and see just how bad things can be and how far you can go in repairing what you have.
http://67-72chevytrucks.com/vboard/s...d.php?t=376589