I would suggest you get another. The cancer is on the inside and will not stop. The water gets in the open ends and bolt holes, and in cases of salt air moisture from marine layer fog along any coastal areas, and areas that use salt on roads for ice control, that water gets inside and the rust starts inside the lower frame. It is a very weak point of the frame now.
When you start welding on it, it will distort and you will be fighting getting it all back together.