[callcoy]

You really should resurface them but keep them bolted together (2 bolts) at the heat riser. If they have been resurfaced several times before you may lose the ability to use your gland rings in the exhaust ports. It is very common for the exhaust manifold to "droop" near the outlet, sometimes so severe that you will not be able to hold a gasket. I have had the best luck with a copper gaskets.