Gadge I'm pretty sure the bore is the same between the Stilo and Coupe, the Stilo has a longer bore
So I would assume the head would be fine off an NA Coupe, turbo may have different cooling and oil passages as you said.
Have you sourced which cams you are going to go for? Here's a set from Colombo & Biriani:
http://www.cb-cams.com/dettaglio_prodotto.php?lang=eng&id_prodotto=71
It's their most aggressive "Road Max" cam, they don't do a "Road Medium" for the 2.4.
I'm looking at getting a set of Max's for my 1.2 soon
I would get rid of both those cats if you're going for fast road cams, you'll be increasing the amount of exhaust gases passing through the exhaust so maybe it would be best for both to be done with? That's just me though, I don't like any restrictions in the exhaust and have gotten rid of mine