If the 85 is a Turbo car, then it will work. If you are looking for something cheap, then try the gas tank repair kit that you find at auto parts stores. I have used it too, and it worked well. Then, save up for a new tank. If this 85 tank is cheap, and I mean real cheap, then you could do that, but just make sure that it isn't going to start leaking on you right after you put it in.
Brian