I substitute a quart of that with the Valvoline Synthetic I run in my D200, stock FT 2-bbl cam in that 360 so I figure that's enough zinc. I get them from Walmart pretty cheap but online might be better.
Duster gets Penn Grade 1 since the 360 in that is quite a bit hotter and is running stock stamped rockers with a .550" lift roller cam.
Either vehicle gets an oil change pretty much once a year or less depending on how much I'm driving them.
