Wow, that looks pretty extensive. There are worse cars in lemons than that but the car being a uni-body all that adds stregth and stiffness. Looking at the last pic you can see where the trailing arm mounts is pretty rusted also. I would forego using it if the floor pans show severe rust also due to the roll cage needing to be mounted to them and a plate inbetween. If you don't have a stable foundation to begin with you'll have all kinds of problems later. Just my thought on it