That cars rusting from the bottom up, that’s why the exhaust and the brake calipers have been replaced, they have already rotted away. The car was originally from Detroit where they use a lot of road treatment in the winter resulting in the rust worm. I would be very wary about a car with that level of corrosion on the underside. You are looking at a body off job to treat it properly. Do you have the time, expertise, space and tools to do that sort of job. Just removing the body from the chassis with that level of corrosion is a job in itself. Potentially it could turn into a money pit. Look around the UK, there are cars better than this one at good prices.