The S4 radiator is significantly different than the earlier models, and the sheet metal attachment points are completely different. It is tilted and the bottom end sits more toward the front of the car as well s having some cooling holes cut in the base. It could be made to fit but a lot of metal work would have to be done.
I have an old IAP aluminum radiator in mine that copies the basic shape and layout of the original radiator, and it does a good job, but I am not not putting out 170 BHP.
I was also looking at some of the Griffin radiators and adapting on of them in. I think it could be done, but there are going to have to be some mods
Mebane, NC yes another one from Mebane and it is not that big of a town.