I think the best way to know is sand blast before making a plan. See what you really have left over. You may need the whole floor.
I wanted just floor pans but had rot all over and in the hump, so the whole floor needed replacing, and all the hat channels. I bought a full floor from Turner 4WD (back in the day) and it was for an M38. There was no CJ full floor available at that time. As mentioned it was sub standard (pretty thin). I had the channels removed and ordered replacements from Classic Enterprise. I also worked close with the welder to ensure my CJ3B floor fasteners remained on the floor vs. using what came with the M38 floor. That required cutting the floor pans almost in half and adding correct caged nuts at certain locations.
One other thing. You'll notice a caged nut in the hat channel under the tank. I believe originally there was a stud there for the frame mount (could use a bolt) but I also had a nut swapped in for the crush sleeve that CE had at that spot.
Once the floor was attached to the hat channels and the floor attached to the tub, you really can't tell.