One of my project heads has surface rust on the mating surface of the intake side. It'* not alot, but it does cover the entire mating surface. Will that be a problem or will the machine shop be able to take care of it?

Wire brush it off and see if it'* pitted. You can't machine that face without upsetting the LIM mating ability.

They should be able to take care of it as long as there is no pitting. You could do it yourself with a little care and a Scotch-Brite pad.

I'd be concerned about the condition of the valve guides if you have rust anywhere.

Well, I looked them over and I don't see any more rust. The rest of the surfaces seemed to keep their oily grime layer from tear down. There is even pools of oil in the recesses of the top of the heads. I guess I managed to clean this face too well.

Hmm, a lot of it comes off if I rub my finger on it.

Cast iron heads tend to rust very quickly, you can almost watch it rust. Chances are the rust is only surface, and has no depth to it.

If you're going to be storing the heads for any length of time (like, for more than a few days), I would recommend a moisture repelling coat of something, like douse it with WD-40. Then, just before installation, dip it.