Stock chain is a 530. Seeing as you need a new rear sprocket/hub and most certainly a chain and maybe a counter shaft sprocket as well.. if there has been that much damage to rear sprocket, it would be behooving to check the front.. You could take this opportunity to convert to a 520 O-ring.. You can read about the conversation here -> http://www.coloradonortonworks.com/catalog/drive.asp.. An excellent place go to remain stock would www.mapcycle.com...... good luck and am interested to know what did tear up those teeth..
530 was fitted the 5 stands for 1/2 inch pitch the 3 stands for 3/8wide. You have now distroyed the whole system so you may as well replace the works with a 520 X ring chain set up. Clubman Racing would be the closest guy to keep all these modifiyed parts in stock. Front and rear sprockets cut down and the chain I use is DID Gold on the sides.