Using cork with RTV is not a good idea. The RTV will act as a lubricant and the cork will slide out from under the intake as you torque it down. If you use anything use something like 3M yellow weatherstrip adhesive and glue the cork to the block with nothing on top of the cork. You'll also want to put a small dab of RTV in each corner where the heads meet the ends of the china walls.
I used that on a cork oil pan gasket on the first 383 I built. When I had to tear it back down later I had a heck of a time getting the remains of the gasket and cement off the block. I haven't used in the 45 years since.
