When anyone sells an item in this country the seller is required to disclose (presumably in writing) all things known about the item that would affect a buyer's desirability to acquire the item or the price paid even if the item sold is "as is".If you sold your car "as is" which is a 1966 vehicle and you knew of nothing wrong with it before the sale, or you disclosed all you knew wrong about it before the sale, you have done what you were required to do.When the new owner comes back to you about the vehicle, you need to advise him there is nothing further for you to do about the vehicle in that he bought a 40 plus year old vehicle "as is" without any warranties, express or implied. At this point, you need to ask him to stop contacting you about the car.Good luck.