well just as it ses up top really, i have some nice retro rims that are 13" by 6 and i need me some rubber for them, i dont really want to stretch the tyers but just want as much grip as poss, just wondering if any of you would have any idea's????

175/50

Or 175/60 if you want to maintain your speedo accuracy. But 175/50 as kam posted would probably be best due to having a smaller sidewall, therefore less tyre flex.