Full quarter panels

I have a question to all on this site. When we put the front clip on we welded the numbers back in the rad support. The front floors and the torsion cross member were replaced. The rear floor on the drivers side needs to be replaced. Now all these panels in the rear are being replaced.

Here's the question.

Why wouldn't getting a rust free 6 cylinder grammas car. and just rebodying the car be a better way to go? I would be welding the numbers in just like I did doing these repairs.

Many critics say no its against the law. But I have done them both ways over the years . Even cut then in half for insurance companies when they were new and wrecked hard. No way this Car will ever be like it was when it was new. Its just new rebody done in pieces