About a year ago I put together a 428 CJ block, C3AE-C heads (406 small chambers) and a 63 Low Riser 2 x 4 intake with a FelPro Gasket set. None of the parts had been machined in any manner that would affect the intake installation, the intake was actually a NOS intake. I had to bend the head gaskets on this combination to get the intake to settle down to where it needed to be to get the intake manifold bolts started. Once I did that it fit up just fine. I did use the corks gaskets on the china wall. At the time I really didn't want to start grinding on the intake as it was NOS, even though it would not have taken much to get it by the head gasket. I think if I could have got all the intake bolts started it would have pulled into place but tweaking the head gasket made it go from difficult to really easy. I guess my point is, at least in my case, even with all relatively virgin factory parts this can be an issue.
