Intake manifold question

[cwolfe]

Hey all, I'm putting a crate 350 in my 65 c10, and I have a question. I planned on pulling the intake from an old 350 and using it. I took it off, cleaned it up, and out of curiosity, put it on a piece of granite that I believe is flat, to see if it was flat. The part that connects to the head looks like it has a slight curve. The ends are touching, but I see a little light under the middle. Is that normal, or do I need to get it machined, or is it no good. Thanks for your help.