Unleaded gas on older cars

I am thinking of buying an older car - 1967 or 1969 Porsche 912. Those old engines were meant to run on leaded fuel - the lead helped the valves to seat easier. What happens if I try to run it on unleaded? Are there lead additives I can add to the fuel (or lead like)?

There are additives that can be purchased. Most auto parts stores carry them. Another thing to consider is that if the engine has been rebuilt, then it is possible that hardened valve seats have been installed, eliminating the need to use a lead substitute. Check with the owner of the vehicle to see if that applies when you look at the car.

Thanks for the reply. Good info. I’ll ask the question.
Thanks again.