O'Day 272 keel
This is not exactly a "timely" reply.... but I only just now happened to see the original question......
The wing keel on the 272s is definitely lead. My understanding from a long time friend and sailing mentor, a guy who had been the local dealer, is that these keels were cast upside down, with the keel bolts pre-placed in the mold.
In casting lead, the dross or slag floats to the top of the pour. The result is a good surface at what becomes the top of the keel where it must smoothly match the fiberglass stub keel. But it yields imperfections and slag inclusions on the bottom of the keel.
I bought my 1987 272LE when it was ten years old. At that point the fairing compound the factory used was falling out. I wound up using a 4 inch disk sander-grinder to take the keel down to bare metal. I then re-faired it and encapsulated it using West System Epoxy and fiberglass..... not a job I would want to undertake again!!!
The first step after stripping the keel to bare metal was applying a thin coat of slow set epoxy, and then while the epoxy was still unset going over the entire surface with a wire brush. That broke up the oxide coating and allowed the epoxy to set into a "tooth" on a true bare metal surface. It is a key step to getting epoxy to bond to lead.
Next came the fairing compound. I seem to recall using the highest density filler West had for the bulk filling, but then switching to one that would be easier to sand and fair for the outermost layer.
And then finally, epoxy with glass reinforcement. I took this up over the stub keel.
It's been over ten years now - the encapsulation is still intact.