I wouldnt do a thing to that car until you have a chance to get a good idea of how much rust is in the car.. You probably havent found all of it yet.
I will bet you that that car right there probably is more time and money in body repair ,then just buying another body.. But if you must have a go at it? I have seen replacement pieces before, I could have sworn LMC or JC Whitney sold the patch pieces and entire panels.
You need a descent Mig with a bottle setup if your gonna do it right. The price of that setup is pretty close to what Crazycuda said the price of a donor or good shell would be..