HOw munch would it cost to fix a 1974-75 nova ss?

My brother owneds a 74 or 75 nova i mean it may even be a 76 it runs and has a good body but the interior and exterior was trrashed by a few kids that he had a fued with i was wondering that if i was to buy this what would be the estimate on how much it would be to fix this car...it has seats and the interior and a good hood but the rest was smashes with a baseball bat and widows were shaddered....