How rough is it? can you feel the grooves if you drag your fingernail across the deck,
I do this on all the blocks I'm putting together. I have a thick piece of aluminum milled flat and I put a piece of sticky back 320 grit paper on it and lightly go over the deck to remove any high spots, then you can really see the grooves. I spray the MLS gaskets with copper a couple times then install them. let it set over night and retorque them. Run the motor and retorque them again. they always turn. ARP says you don't have to retorque them, Cometic says no retorque but with aluminum heads they do move around more than iron so they need to be checked every so often anyway.
