Its hard to say what it would cost. Rust repair gets expensive fast which is why I bought a car from California. If it needs 1/4 and rockers, It may need outer wheel wells too. Also check were the trunk extensions meet the 1/4s, If it needs lower 1/4s it probably needs trunk extensions also. Now your painting the entire back half of the car. I would also take a good look at how they filled the side marker lights.
What carb is in the 340. The valve covers and exhaust look like 70 or early and the carb looks to be a AVS which would also be 70 or earlier.
