71 dart rust!!! help

While it is possible to open those holes a little more then weld it back up, its not the easiest thing to do. In some cases it mat be better that you cut a small chunk out and then weld a new piece in. Seems that may be the case on that bottom corner. The metal seems to be pretty far gone there. If you just take to spot welding it, you will probably burn through it pretty quickly, if you dont have the experiance needed. However it is definately possible to just spot it closed, very carefully. Just depends on your skill and welder type.