Consider an all brass/coppper aftermarket replacement. I bought a good aftermarket radiator from a place in texas that advertises in the star. Here is a copy of their ad:
New Radiators: for 280/380/450/560SL, W107 chassis; W124 chassis, heavy-duty, 300E/CE/TE. Tigris International, Box 42408, Houston, TX 77242; 713/628-1362;
tigrisint@yahoo.com.
The one I got was about $300 including shipping...in my opinion it is much better than the plastic/aluminum ones made by Behr and Valejo and less expensive too. Mine didn't break at the neck but a seam along the side where the plastic is crimped to the aluminum was weaping...another common fault. At least with this brass/copper unit I can get it fixed if it starts leaking but it has been in there over a year so far with no trouble.