I found and resurrected this thread because the top of my keel had pin-holes in a blistered loose area that was raised from the profile of the top surface. So for those who find this in the future . . .
I finally called Mars and spoke to Bill Souter, their Chief Technologist. He has no experience with the 322 and said the only person who might remember would be the company President, who I wasn't going to bother. He also said that if Mars made the keels the molds for something as old as our boats those molds would have been discarded long ago, so replacements would be one-off and very expensive.
What I wrote about seeing what looked like ceramic in the wing of another keel does not apply to the O'Days. According to Mr. Souter, the wing is indeed solid lead.
As for the blistered area on the top surface, he said that no lead is without some amount of dirt & other impurities and one of the problems with casting a wide flat keel is that whatever dirt is in the lead will float to the top. With a wide flat wing, the impurities can collect like a bubble that hardens before it gets to the vertical portion of the keel and he said the fix is to simply grind it out and fill it with epoxy.
I did and it will look like new when done. It is a bit nerve wracking though to make like a dentist, grinding the loose brown dirt back to find the good material then tapering the edges of the hole out. The deepest point was about a half inch.