327 exh gaskets

They came out of the factory without gaskets. If it didn't have gaskets on it when you took it apart then it's likely never had gaskets and you can reassemble it without gaskets if the surfaces look good still. Bolt them up to the heads and poke around with a feeler gauge to see if there is gapping. 

It's game over once they're bolted on with gaskets because the gaskets allow the manifolds to warp slightly and then they never seal without a gasket again. 

Forget having them milled flat. Nobody seems to be able to do it right. I've ruined several perfectly good manifolds by asking machine shops to mill them flat. Nothing good has come from it. 

But yes, try to assemble it without gaskets if you can. No gaskets equal less places for exhaust leaks to form. My driving style tends to blow gaskets so I prefer to not have gaskets if I can get away with it.