I haven't used synthetic oils in any of my "classic cars" over the years. It has always been conventional oils. In my current 418" small block Duster, (with a Bullet Racing solid cam .250 @.050) I have used Gibbs Driven oils with a Wix filter.
If I can't get Gibbs, I will use Royal Purple with Rislone zinc additive. Oil pressure is great and has zero problems
