I have had some luck restoring old batteries......Granted, they were not totally dead, but its worth a shot.
What you do is drain out all the old battery acid and replace it with a distilled water/Epsom salts mixture. Take a pan of water (2 quarts), heat it almost to a boil and ad about 8 tablespoons of Epsom salts and mix in.....Then put them on a slow charge (2 amps) for a day or so, I have restored 3 garden tractor batteries this spring that would not hold a charge anymore. How long they will last, I dont know yet