Something else to keep in mind also. I have seen the front and rear cork end gaskets prevent the sides from sealing properly if you have too much crush. Better to have no crush at all and a little silicone. Rather than machine the bottom of the intake, I would throw those end gaskets away and just use silicone. 90 degree surfaces should work fine. Proper intake manifold fit is one of the hardest things to get accomplished on an FE.