As others have already pointed out, give the entire car a good thorough inspection before you start sinking any more money in it. Make sure that there are no major rust issues with the body, floors, trunk and frame (especially the frame rails behind the rear wheels). If those areas look good, then I would say go ahead and start on it. In terms of the chassis, suspension and brakes, most '78-'88 GM A/G body cars are the same. In most cases, what works for a 2 door, will work on a 4 door or wagon. I would say, see what needs to be done to the car as it is, to getting it up and running safely first, then do modifications that will make it more enjoyable for you and your son, that are within your means. Have fun with it.