Valve Cover spacers

Looking for some guidance here. I want to run fabricated valve covers on my 408 stroker with Victor 340 intake manifold. I know the valve covers will not clear the intake and rather than notching the valve covers, I would prefer to run a valve cover spacer. My question is, what is the minimum height spacer I need to clear the Victor 340?

Thanks in advance,
Bill
I have fabricated valve covers on my Trickflow heads and the covers clear my Indy cylinder head single plane intake. Sorry I know thats not a answer. I would recommend you contact Pittsburgh Racer. He runs that intake and he might know the answer to your question