My father in law has a 66 Pontiac GTO with the 389 and a 4 speed. Last year he had the motor machined along with new pistons. He also had a frame off restoration done in 2012. Right now he's got Brad Penn 30 weight break in oil in it as per the machine shop that re did the engine. Some facts about the car: He does about 500 to a 1000 miles a year The engine is bored over 30 with a flat tappet cam He only uses an AC Delco PF24 oil filter He does change it about once a year He likes Pennzoil 30 weight oil but it was used before the engine was re done. My father in law isn't sure what to use but wants to use an oil that has zinc in it for the cam. The Brad Penn has been in there since last year and has the itch to change it. If anyone has a recommendation it would be greatly appreciated and thanks in advance, Steve.