Coming off Letro and Using Arimidex

So I had a run in with gyno. Used a reverse gyno protocol that seems to have worked perfectly. As I finish my taper off letro I want to switch to arimidex. Can anyone clarify what the transition should be? Thinking of Dex .25mg eod sound right? Do I need to run nolva with it?
I’m 190, 400 cyp a week, 8-9% bf, thanks for any input or direction.