Typical C-460 intake installation

Is it typical to have to mill a new C-460 intake to get proper fittment to the heads. I purchased a brand new intake and I was going to send it off to be ported, I removed the sheetmetal and was checking to make sure everything lined up properly and its not even close. I clearenced the top edges where it was contacting the heads near the gasket rail of the heads and it got better but still not very close. I used an angle finder and it has the same angle as the sheetmetal intake, I am guessing at this point the heads have been angle milled or rolled. What are some opinions of a path foward from here. Thanks.

IF the head surfaces have been modified then you will need to modify the intake manifold.

Or the deck surface. If the heads have been ported the ports could have been moved also.