......oh man. With holes like that, in such open places, I'm afraid to ask what your undercarriage is like. Rust this bad is like cancer, if it's spread too far, there might not be any hope of bringing it back. Because you can't weld rust, and you cant weld "to" rust. You have to start by striping all the way down to bare metal, to find where the rust stops. Then you need a donor car to cut and chop from. You might start stripping and find that the rust just keeps going, through and through. If that's the case, then there is just no bringing it back. It would cost SO much, that it would have been the same as buying and restore painting 3 other shells.
As far as price gos. I say your looking at an easy 2 thou. That is, if you don't find anymore. Here is what I would do first.
Step 1.) Locate ALL rust arias.
Step 2.) Take an angle grinder with a wire wheel and strip down to bare metal.
Step 3.) Assess the depth and distance of each rusted aria.
Step 4.) Determine the fate of the car based on the percentage of body that is un-fixable ...ie "cut and weld". Considering the price of a donor shell and the tools + time involved.
If the rails of the uni-body have holes like that, then the fate of your ride is sealed. Good luck man.
to all who are cancer sensitive, "including myself". No, disrespect was intended.