I agree with BLK65,
I spent a long time looking. budget started around the same money. Seemed they all were going to cost a bomb to bring up to spec.
I just got mine a few months ago.. No rust, matching panels, gun barrel straight. cost me 480 to RWC. for the extra, it was more than worth it. Had its first outing at the claytons and got great feedback.
I think you need to work out your total spend and look for one close to that. There will always be extras, but thats the beauty of a mustang, you just have to make it better.
good luck