The rear floor section was not just spot welded to the CJ-6 extension panel in front of it. From the factory, the rear floorpan was first hooked onto the mid-floor brace and welded, and then the mid-floor panel was installed and welded over top of the rear floor. The rear floor had to be cut away so that the other spot welds could be accessed. Don’t get too rough and just start ripping things out if they don’t come out easy. There’s a chance you missed some welds somewhere. Do some investigation and form a plan of attack.