The Focus RS uses a Newer version (GT Series) Turbo, Smaller in size in comparison to the equivelant old (T) Turbo, the have roller bearings and in general are far more efficiant(sp?)... I'm not sure a T4 would actually fit, and if it did to be honest i'd gess it would be far too 'laggy'.

As for the Cossie I/C I doubt it would fit mate, the Pro Alloy one for instance has been specially designed and comes with all the mountings etc...

have a look here > www.turbodynamics.co.uk for info on the turbo

and here > www.proalloy.co.uk for the intercooler