I'm afraid that I would have to disagree with Mr. MacGregor. Almost anything can be repaired with the right tools, a little forethought, and a lot of patience. I have a 22' MacGregor and am just beginning a restoration on it. It will need the keel rebuilt along with just about everything else. Here is a link to some information on keel repair.
http://www.macgregor-boats.com/gilbert/external.html