You've given so little info. Please tell us a little more about this "basically stock" engine. After 50 years, there are very few stock engines. Usually someone has been in them before and made some changes. If you are not the original owner, or have not owned the car/motor for 35 years, be skeptical that the motor is stock.
What is the engine size?
What is the measured compression ratio?
What is the cranking cylinder pressure?
Generally speaking, factory heads with unknown detailed history are likely weak performance wise, and any new aftermarket aluminum head will give a noticeable boost in power.