The simplest way to convert your car to run on unleaded fuel is to put it in the tank.
Lead in petrol performs no function until it is burnt, when it then acts as a protector for the exhaust valves and seats. Good quality exhaust valves and seat inserts make sure that the valves cannot receed into the head, but with most old engines the valve seats are so hard anyway that putting unleaded fuel in will make very little difference.
If a valve should wear (or receed) then replace the valves and have the seats inserted or have a reconditioned engine unit.
Apart from the exhaust valves and seats, no other parts need to be changed from standard - even the timing stays the same.
Some very high compression engines may require 98 octane but we run a variety of 4 cylinder engines on the 95 octane with no problems.