Big Block headgaskets - steel shim for racing?

You may not like that gasket for NOS. You want to make sure the gasket has adaquate bore size for the 400's largest bore of any big block, and that the fire ring does not sit out beyond the cylinder's taper. The 1009 fits ok (4.41 bore, your block at .030 over is 4.38). Otherwise you can burn them out in a few miles. The steel gasket with it's smaller bore will also act similar to a sharp edge, and could promote preigition if you are not careful.