I don't know if you are looking to upgrade or just replace your stock piece....Fluidyne, does not make a Radiator for the 4th gen.
You can order a C&R kit with electric fan from modacar.com:
C&R radiator + fan $399
or
There are other 55mm (2.25 in) radiators available out there such as:
phase2motortrend (KOYO: (925)516-2695 call and order direct for a few bucks savings...)
But they usually don't include the fan too. I'm in the market myself to upgrade the cooling capacity (January, grad student grant $), so I've been doing some of research. So far, the modacar.com deal appears to be the best. Thin line high flow fans run about 95-100.
Keep us posted