Another jwillie70 1970 Datsun 240Z post...
Before putting in the new floorpans I had to cut out the old ones. I did them one side at a time to keep the car rigid. It is a unibody and the floor is an intragral part of the overall stability of the car. I needed a clean edge to weld the new floors to so I used a cutting wheel instead of a torch. Below are some shots of the floor removed from the front and the rear
The passenger side was first. It was a real pain since I had to beat the *&%!@ out of the transmision tunnel to get the six speed to fit. This caused the tunnel wall not to line up very well with the new floor. In the end I won and got it tacked in all around from the top.
The drivers side was next, but this time I had some experience and it went a little smoother. I think you would have to agree that the floorpans HAD to be replaced.