4THGEN- I don't know for sure if the Monte lower hose will clear or not. Never tried it. I was going off a recoomendation from another person that had done it and was told to use that particular lower hose so it would clear the belt and pulleys. If the Monte hose routes away from the belt as well then good to know.
As far as headers and this rad. I don't see why not. It may be close but not interfering. If I can ever save up some extra $$ I'd like to get a set of headers on my GT, even though it's not S/C'd I don't see why it wouldn't hurt to help the flow.