Hello new member here. Got a new to me 1980 Chevrolet pickup with a 350 V8 and only 44k miles on it. I understand this is a flat tappet engine and the oils in it’s heyday had enough phosphorus to protect the cam. However oils today have significantly less...the practical solution is to use a high zinc oil such as Amsoil 10w40 or Mobil 1 0w40, BUT this truck also has its factory catalytic converter which I don’t want to ruin either. Currently running Mobil 1 extended performance, but I’m worried about that flat tappet cam becoming worn while trying to keep the converter happy.. What do you guys suggest? And no I really don’t want to run that Castrol 20w50 “Classic” oil as a 20w50 is too thick.