How can you find out if a car that you had 40 years ago is still on the road?

If you know the vin number, you can enter it at Car Fax and it will tell you if the car is on the road. I don't know if they can find a car for you if you don't have current information, but you can try. You might be able to do it by asking about it through car clubs for that kind of car or classic car clubs.