Refer to my earlier post #13. Do you know that you need to replace both cores. The smaller core is at the front and is most prone to damage. When I had mine re-cored they tested the rear core when they split radiator casing and that was fine so they just replaced the smaller front core. Don't forget to replace 3 hoses that connect the two cores on near side with silicon pipes - you never know it may be just the rubber hoses and clips that have failed which is a relatively small cost - unfortunately you will only know for sure once you or your rad specialist remove the casing that houses the two cores.
Has anyone tried the "Ordonez" referred in this thread?
http://www.sportsmaserati.com/showthread.php/51-Alternative-parts-what-everyone-needs-to-know/page51