50 year old car, huh. Flat-tappet? As an AMSOIL Dealer I have an oil called ZROD that includes additives like zinc and phosphorus to protect older engines. It is currently made in a 10w30 or a 20w50. To read more about it go to http://www.amsoil.com/storefront/zrt.aspx
If you have any questions feel free to send me a PM.
