I think you are making a lot of unnecessary work for your self when rads are out there at dirt cheap prices..

Fiat Stilo Radiators - Euro Car Parts UK?s No.1 Car Parts Retailer

In theory, as the front end of the 2 cars are the same, the two SHOULD be interchangeable.
The only worry I'd have is about getting the piping to fit, you'd have top get one coolant hose to cross the exhaust manifold, so unless you get it nice and tidy it'll burn through in no time.

If you've already got the 2.4 rad, give it a go, can't hurt!

Is it a possibility to get yours recored? That should be about £40-£60 all in, probably cheaper than the new pipework, fixings and pain you'll go through to get a 2.4 rad to fit?

Hey up mate ,you shouldn;t need too much new pipe work, and iirc, you needn;t worry too much about which way round you fit the pipes to yoru new Rad, cause most radiators are a routed system anyway, in that the coolant flows through a set course in the veins of the, so as the coolant is ahem... cooled, as it passes through the miles of veins, by teh air passing over it (Fan assisted or not) then it maters not which way you connect the pipes, so i would suggest whatever is easiest.
Of course Andy makes a good point, about the Exhaust mainfold.
Not point cooling the water only to heat it up again on the exhaust, oh and run the risk of melting the bloomin pipe work.

But sensible routing of new lopng enough and appropriately shaped hose and you should be COOOOOOOLLLL (pardon the pun)
Good luck mate and keep us updated

Originally Posted by Andymac

Is it a possibility to get yours recored? That should be about £40-£60 all in, probably cheaper than the new pipework, fixings and pain you'll go through to get a 2.4 rad to fit?

My link gives him a new rad for £60.. dont think its worth all the hassle fitting the 2.4 rad with all the problems that might occur getting it to fit..I'v had 35 years of modding cars and getting things like this to fit can some times be a right pain in the arse to say the least..might seem simple from the outset but there is always something that hacks you off..why struggle when there isnt any need to..leave the car as it is until you source a second hand one or can afford a new one..