You can purchase a new all aluminum radiator built for any MB. I called the folks this morning - Griffin Radiator (800) 722-3723
They do not have any "off the shelf" units for my E320 - the lady said I would have to send her my radiator and they can build an exact duplicate of it in all aluminum. She indicated that right now it would take about six weeks and she could not give me a firm price but indicated to plan on spending between $900 and $1200. I saw one of their radiators in a fastback Mustang this weekend and it looked like a very high quality item.