In my opinion, if it's rusty, cut it out, make up a repair and weld it in. If your not confident, having a go yourself, find someone who is. I would be surprised if you will be able to find those sections in good order on a breaker, as those areas appear to be common areas to rust. I had to make up similar repairs on 'tiny's' V8 Sapphire, along with a herd load of others.
Keep on, keeping on, it'll be worth it in the end