If your asking about SB aluminum valve covers?
Sometimes with some intake manifolds, I think mostly stock manifolds you have to clearance the lip some on the intake side of the cover.
Here a couple of crappy pictures of some old valve covers I used to run. I had to grind on them in 2 places to get them to clear the intake manifold. Actually I was just thinking they were like that(ground on) when I got them and I only did the baffle. They were used when I got them.


Here's how I handled my PCV valve baffle, I did this a long time ago, it worked well. Maybe not the best, but worked.

I think those little square things sticking out interfere with the valve covers?