Yea', he's right, I'd have both heads cleaned up, this does not mean milling, just means a re-surface job only taking off a few thousands, enough to clean them up (the same).   Problem will milling off very much is, that this shrinks the match between the intake manifold holes, a little is OK but .... not much.   A re-surface job is quick, simple and doesn't cost much.   Milling is a while different story, requires a setup and this takes time .. and money.
Your heads will be fine.

warren 

Since it crosses the fire ring of the gasket, it would be better if the head was re-surfaced to remove the imperfection.  You will need to cc the combustion chambers in both heads and cut both so that they will be equal.  Easier to do it now rather than having to tear it down again.  Peace of mind is worth the bother.  Joe-JDC

JDC

I'm finally getting back to building my new engine for my truck.  After tearing down a 312 with a broken web,  I put the heads up on the shelf.  I took them down tonight to clean them up.   When I pulled the head gaskets off,  I found a scratch in 1 head that starts in the  combustion chamber,  and goes all the way to the oil galley in the head.  I can't catch my fingernail on it,  and it was under the head gasket, so it was there when whoever assembled the last engine.   The 312 they came off of was never fired,  and I have paperwork showing they were rebuilt.   Would a Fel-Pro gasket seal this?   If I copper coat it would that give it a better seal?   Or do I need to get this head milled?