Hi John, I've just seen the photo's, I think that by the time you grind back to solid metal you're going to be left with a large pile of grinding dust, and very little else. If they were mine, I don't think I would spend the time and money getting them fixed. I've scrapped better condition exhaust systems than that, it's up to you but I would think it would be easier to find some in better condition.
Jez